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A dictionary of applied ctiemistry, 




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A DICTIONARY 

OF 

APPLIED CHEMISTRY 



VOL. III. 



A DICTIONARY OF APPLIED CHEMISTRY 



SIR EDWARD THORPE, C.B., LL.D., F.R.S. 

Assisted by Emitunt CoMtributors 



REVISED AND ENLARGED EDITION 



IN FIVE VOLUMES 
Containing upwards of 6000 Articles, many w 

Vol. I. A-Che 

Vol. II. Chi-Qo 

Vol. III. Gr-Oils 

Vol. IV. Oilstone— Soda Nitre 

Vol. V. Sodium-Z 



th Illustrations 



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LONGMANS, GREEN AND CO. 
LONDON, NEW YORK, BOMB.'^Y, CALCUTTA, AND MADRAS 



A DICTIONARY 



0¥ 



APPLIED CHEMISTRY 



BY 
Sir EDWAED THOEPE, C.B., LLC, F.E.S. 

XIMEBIXUS FBOFESSOR OF QBNBaAL CHEMISTBT AND DIBBCTOB OF IBB CHEUIGAL LABOBATOBIBS 
OF TUB lUPEiaAC COLLEQB OF SCIBNCB AND TRCHKOLOGT, SOUTH EENSINQTON, LOHDOH; 
LATE FKINCIPAl, OF THE a0VBB»UENT I.ABOBATORT, AND A TAST PSESIDSNT bff 
THE CHEUIOAI, SOOlBir AND OF THE SOCIEXT OF CHBMECAL INDUSTBT 



ASSISTED Bl EMINENT CONTBIBUTORS 



IN FIVE VOLUMES 



VOL. in. 



REVISED AND ENLARGED EDITION 



WITH ILLUSTRATIONS 



NEW IMPBESSION 

LONGMANS, GREEN, AND CO. 

39 PATERNOSTER ROW, LONDON 

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1919 

All rights reserved 



ABBEEVIATIONS 

OF THE TITLES OF JOURNALS AND BOOKS. 



Amer. Chem. J. 
Amer. J. Pharm. 
Amer. J. Sci. 

Analyst . . . 
Armalen . . . 
Ann. CMm. anal. 

Ann. Chim. Phys. 
Ann. Falsi/. . . 
Ann. Inst. Pasteur. 
Arch. Pharm. . 
Bentl. a. Trim. 

Ber , 

Ber. Deut. pharm. 

Ges 

Bied. Zentr. . . 

Bio-Chem. J. 
Biochem. Zeitsch. 
Brewers /. ■ . . 
Bull. Imp. Inst. 
Bull. Soc. chim. 
Chem. Ind. . . 
Chem. News . . 
Chem. Soc. Proc. 
Chem. Soc. Trans. 
Chem. Zeit. . . 
Chem. Zentr. 
Gompt. rend. . . 
Dingl. poly. J. . 
Farber-Zeit. . . 
FlUcJc. a. Hanb. 

Frdl 

Gasn. chim. ital. 
Jahrb. Min. . . 
J. Amer. Chem. Soc. 
J. Ind. Eng. Chem. 
J. Inst. Brewing 
J. Pharm. Chim. 
J. Phys. Chem. . 
J.pr. Chem. . . 
J. Buss. Phys. Chem. 

Soc 

J. Soc. Chem. Ind. 
J. Soc. Dyers. . 
Min. Mag. . , 
Monatsh, . . . 



Pharm. J. . . 
Pharm. Zeit. 
Phil. Mag. . . 
PhM. Trans. . . 
Phot. J. . . . 
Proc. Boy. Soc. . 
Bee. trav. chim. 
Zeitsch. anal. Chem. 
Zeitsch.angew.Ghem. 
Zeitsch.a/norg. Ghem. 
Zeitsch. Nahr. 

Gemcssm. . . . 
■ Zeitsch. offentl. 

Chem 

Zeitsch. physikal. 

Chem 

Zeitsch, physiol, 
Chem, . . o • 



American Chemical Journal. 

American Journal of Pharmacy. 

American Journal of Science. 

The Analyst. 

Anualen der Chemie (Justus Liebig). 

Annales de Chimie analytique appliqu^e al'Industrie, &l'Agrioulture, 

a la Pharmaoie et i la Biologic. 
Annales de Chimie et de Physique. 
Annales des Falsifications. 
Annales de I'Institut Pasteur. 
Archiv der Pharmazie. 
Bentley and Trimen. Medicinal Plants. 
Beriohte der Deutsohen chemisohen Gesellschaft. 

Berichte der Deutschen pharmazeutisohen ijcsellschaft. 
Biedermann's Zentralblatt fiir Agrikulturchemie und rationellen 

Landwirtschafts-Betrieb. 
The Bio-Chemical Journal. 
Biochemische Zeitschrift. 
Brewers Journal. 

Bulletin of the Imperial Institute. 
Bulletin de la Sociit^ chimique de France. 
Chemisohe Industrie. 
Chemical News. 

Journal of the Chemical Society of London. Proceedings. 
Journal of the Chemical Society of London. Transactions. 
Chemiker Zeitung, 
Chemisohes Zentralblatt. 

Comptes rendus hebdomadaires des Stances de I'Acadtoie des Sciences. 
Dingler's polytechnisches Journal. 
Far ber- Zeitung. 

Fluckiger and Hanbury. Pharmacographia. 
Friedlander's Fortschritte der Teerfarbenfabrikation. 
Oazzetta chimica italiana. 

Neues Jahrbuch fiir Mineralogie, Geologic und Palaeontologie. 
Journal of the American Chemical Society. 
Journal of Industrial and Engineering Chemistry. 
Journal of the Institute -of Brewing. 
Journal de Fharmacie et de Chimie. 
Journal of Physical Chemistry. 
Journal fiir praktische Chemie. 

Journal of the Physical and Chemical Society of Russia. 

Journal of the Society of Chemical Industry. 

Journal of the Society of Dyers and Colourists. 

Mineralogical Magazine and Journal of the Mineralogical Society. 

Monatshefte fur Chemie und verwandte Theile anderer Wissen. 

schaften. 
Pharmaceutical Journal. 
Pharmazeutisohe Zeitung. 

Philosophical Magazine (The London, Edinburgh and Dublin). 
Philosophical Transactions of the Royal Society. 
Photographic Journal. 
Proceedings of the Royal Society. 

Receuil des travaux cbimiques des Pays-Bas et de la Belgique. 
Zeitschrift fiir analytische Chemie. 
Zeitschrift fiir angewandte Chemie. 
Zeitschrift fiir anorganische Chemie. 

Zeitschrift fiir Untersuchung der Nahvungs- und Genussmittel. 

Zeitschrift fiir offentliche Chemie. 

Zeitschrift fiir physikalisohe -Chemie, Stoohiometrie und Verwandfr 
schaftslehre. 

Hoppe-Soyler's Zeitschrift fiir physiologische Chemie, 



LIST OF CONTEIBUTOES 

TO VOLUME III. 



Dr. B. F. ARMSTRONG (late of Messrs. Huntley and Palmers, Reading). ' [Inositol ; 
Ihvertasbi; Lactase; Lipase; Maltasb,] 

Dr. P. PHILLIPS BBDSON, M.A., F.I.C., Professor of Chemistry in the Armstrong College 
of Science, Newcastle-on-Tyne. [Lead, MetaijLUBqy of.] 

G. S. BLAKE, Bsct., A.R.S.M. [Magnesium.] 

HAROLD BROWN, Esq., Th£ Imperial Institute, London. [Guita Pbrcha.] 

Dr. J. C. GAIN, Editor of the Journal of the Chemical Society, London. [Htdsoxy- 

QUINONE OOLOUBING MATTERS ; INDULINEB ; METHYLENE BLUE ; METHYLENE GrEEN.] 

B. G. CLAYTON, Esq., P.I.O, [Matches.] 

JAMBS OONNAH, Esq., B.A., B.So., P.I.O., The Government Laboratory, Custom House, 

London, E. [Kibschwasseh ; Liqueurs and Cordials.] 
CECIL H. CRIBB, Esq., B.So., P.I.C, Consulting and Analytical Chemist, London. 

[Mace; Mustard; Nutmeg.] 

Dr. ARTHUR W. OROSSLEY, P.R.S., P.I.O., Professor of Chemistry, King's College, 
London. [Nitrogen, Atmospheric, Utilisation of.] 

Professor EDWARD HART, Lafayette College, Easton, Pa., U.S. America. [Nitric Acid, 
Manufacture of.] 

Dr. G. G. HENDERSON, M.A., F.R.S., P.I.C, Professor of Chemistry, Boyal Technical 
Cpllege, Glasgow. [Iodine.] 

Dr. JOHN T. HEWITT, M.A.f P.R.S., Professor of Chemistry in the East London College. 
[Ketones.] 

GEORGE T. HOLLOWAY, Esq., A.R.O.S., P.I.C, Metallv/rgical Chemist, London. 
[Molybdenum.] 

Dr. JULIUS hUBNBR, M.So., P.I.C, Director of Dyeing amd Papermaking Departments, 
Municipal School of Technology, Manchester. [Mercerising.] 

HERBERT INGLE, Esq., B.So., P.I.C, late Chief Chemist to the Transvaal Agricultural 
Department. [Grape ; Grasses ; Guava ; Horse-radish ; Kohlrabi ; Leek ; Lemon ; 
Lentils ; Lettuce ; Linseed ; Liquorice ; Lupines ; Maize ; Manqel-Wurzel ; 
Mango; Manna; Maple; Marjoram; Medlar; Melon; Millet; Mountain Ash; 
Mulberry; Mushroom; Nuts.] 

Mrs. KAHAN-COATES, B.So. [Lithium.] 

Professor EDWARD KINOH, P.I.C, late of the Boyal Agricultural College, Cirencester. 
[Legumin.] 

Dr. JULIUS LEWKOWITSOH, M.A., P.I.C., late Consulti/ng and Analytical Chemist, 
London. [Grape Se£d Oil ; Greases ; Hemp Seed Oil ; Herring Oil ; Jamba Oil ; 
Japanese Sardine Oil ; Japan Wax ; Lard ; Labd Substitutes ; Laurel Oil ; 
Linseed Oil ; Maize Oil ; Margarine ; Menhaden Oil ; Myristioa Pats ; Myrtle 
Wax ; Neat's Foot Oil ; Niger Seed Oil ; Oils, Fixed, and Pats.] 

Dr. GILBERT T. MORGAN, P.R.S., A.R.C.S., P.I.C, Professor of Chemistry in the City 
and Gmlds of London Technical College, Finsbury. [Lanthanum ; Lutecium ; 
Neodymium.] 

A. G. PBRKIN, Esq., F.R.S., P.I.C, Clothworkers' Besearch Laboratory, University of 
Leeds. [Green Ebony; Indian Yellow, Piuri, Purree or Pioury; Indigo; 
Natural ; Jax-wood ; Kamala ; Kebmeb ; Lac Dye ; Lakes ; Lecanoric Acid ; 
Lichens ; Litmus ; Logwood ; Lokao ; Lonohooarpub ; Lotus Ababicus ; Madder ; 
MoRiNDA Oitrifolia; Morinoa Longlfloba; Mobinda Umbellata; Munjbet; 
JIyeica Nagi ; Nycanthes Abboe-Tbistis.] 



^11 LIST OF CONTRIBUTORS. 

Professor W. H. PERKIN, LL.D., F.R.S., and Dr. ROBERT ROBINSON, Chemicai 
Department, Universities of Oxford and Liverpool. [Methyl Antheacenb and otheb 
Alkyii Debivatives of Anthbacene.] 

Professor H. R. PROCTER, M.Sc, P.I.O., The University, Leeds. [Leathee.] 

H. DROOP RICHMOND, Esq., P.I.G., late Chemist to the Aylesbury Dairy Company, 
London. [Milk.] 

Sir THOMAS K. ROSE, A.R.S.M., T}ie Boyal Mint, London. [Mebcubt, Mbtalltjbgy 

OP.] 

Dr. WALTER ROSENHAIN, P.R.S., The National Physical Laboratory, Teddington. 

fMBTAPLOQBAPHT.J 

Dr. p. W. RUDLER, I.S.O., late of the Museum of Economic Geology, Jermyn St., London. 
[Granite ; Jabpeb ; Lemnian Eabth ; Mabblb ; Obsidian.] 

FRANK SOUDDER, Esq., P.I.O., Analytical and Consulting Chemist, Manchester. 
[Meat Exteacts.] 

Dr. ALFRED SENIER, P.I.C, Professor of Chemistry, University College, Galway. 
[GuARANA ; Gtim Besins ; Gums ; Habmala ; Hemlock ; Henbane ; Hoese-Chest.. 
not ; lODOFOEM ; lODOLE ; IPECACUANHA ; Jaborandi ; Jdnipee ; Kino ; LACTnoAEiCM ; 
Laudanum ; Laubus Nobilis ; Ledum Palustee ; Liquobice Root ;' Lobelia ; 
Mabbubium ; Mucilage ; Musk ; Nox Vomioa.] 

Ii, J. SPENCER, Esq., M.A., Mineralogical Department, British Museum, London. 
[Gbaphite ; Gypsum ; HiJSMATiTE ; Hallyosite ; Hiddenite ; Hollandite ; Ilmenitb ; 
Iodyeite ; Jade ; Jamesonite ; Jet ; Kainitb ; Kaolinite ; Kieselguhb ; Kiesebite ; 
KuNziTE ; Lapis-Lazuli ; Lava ; Lazulite ; Lbadhillite ; Ledcitb ; Limestone ; 
Limonite ; LiTHOGBAPHic Stone ; Lithomaege ; Loadstone ; Lydian Stonb ; 
Maqnesite ; Magnetite ; Malachite ; Manqanitb ; Maecasitb ; Mabl ; Meeb- 
sohaum, mlaeqybite ; mica ; mispickel ; molybdbhitb ; monazitb ; mothbe-of- 
Peael ; Natrolite ; Nateon ; Niteatine ; Ochbe.] 

Dr. J. J. SXJDBOROUGH, F.I.C., Professor of Chemistry in the Indian Institute of 
Science, Bangalore. [Hydbolysis.] 

Dr, JOCELYN F. THORPE, P.R.S., Professor of Organic Chemistry, Imperial College 
of Science and Technology, South Kensington. [Hydbazines ; Hydeazohbs ; Indan- 
THBiiHB; Indbnb; Indoles; Indoins; Indozyl Compounds; Lactones.] 

Professor THOMAS TURNER, M.Sc, A.R.S.M., P.I.C, The University, Birmingham. 

[lEON, MeTALLUEQY OP.] 

JOHN CHARLES UMNEY, Esq. (Messrs. Wright, Layman & Urnney, London). 
[Oils, Essential.] 

Dr. MARTHA A. WHITELEY, A.R.O.S., Lecturer in Organic Chemistry, Imperial College 
of Science and Technology, South Kensington. [Guanidine ; Guanine ; Heteeo- 
XANTHiNE ; HisTiDiNE ; Hydantoin ; Hydubilic Acid ; Hypoxanthinb ob Saecine ; 
Leucine ; Lysine ; Malonio Acid ; Mueexidb ; Murexoin.]^ 

Geheimrat Professor Dr. OTTO N. WITT, late of the Polytechnic, Charlottenburg, Berlin. 
[Ihdamines and Indophenolb ; Indigo, Artificial, and Indigoid Dyestupfs.] 

Dr. W. P. WYNNE, P.R.S., P.LO., A.B.C.S., Firth Professor of Chemistry, University of 
Sheffield. [Naphthalene.] 



NOTE TO BINDER. 
Plates 1 and 2 to face pages 461 and 467 respectively. 



DICTIONAEY 



OF 



APPLIED CHEMISTEY. 



GRAIN LAC V. Lac resins, ait. Resins. 

GRAIN OIL V. Fusel oil. 

GRAIN TIN V. Tin, 

GRAINS OF PARADISE v. Cocculus m- 
Diotrs. 

GRANITE. A holoorystalline acid rook of 
plutonic origin ; i.e. it is a rock consisting 
wholly of crystalline minerals, and containing 
from about 60 to 80 p.o. of silica, partly free 
and partly combined, whilst its texture suggests 
that it has slowly consolidated from a molten 
condition, under great pressure, at considerable 
depth beneath the surface. Granite is essen- 
tially an aggregate of felspar, quartz, and 
mica. The usual felspathic constituent is ortho- 
elase, or common potash-felspar, generally asso- 
ciated with more or less plagioclase ; aud the 
mica is either muscovite (white mica) or biotite 
(dark mica), whilst in many granites both micas 
are present. Biotite-granite is now frequently 
known by G. Rose's name of granitite. Granitic 
rocks may contain various accessory niinerals, 
such as hornblende, augite, and tourmaline, thus 
giving rise to varieties often distinguished by 
special names ; whilst, on the other hand, it 
sometimes happens that one of the minerals of 
typical granite may disappear, thus producing a 
binary granite. Aplite is a name occasionally 
applied to a rock consisting only of felspar and 
quartz ; but sometimes extended to all musco- 
vite-granites. If the quartz and felspar are so 
intergrown as to suggest they have crystallised 
simultaneously, the rock is termed graphic 
granite or pegmatite. Under the name of greisen, 
Geri^an miners recognise a rock composed of 
quartz and mica, usually carrying topaz, and 
associated with tin-stone. An aggregate of 
orthoclase and black mica is known as mica- 
syenite ; the typical syenite, sometimes distin- 
guished as horrdilende-syenite, being composed 
essentially of orthoclase and hornblende. Horn- 
blende-granites are often called, by English 
writers, ' syenitic' Schorl, or black tourmaline, 
is not unfrequently present in granite, especially 
near the margin of intruded masses. Garnet is 
an occasional constituent, but not so commonly 
in true granite as in granulite, a rock consisting 
mainly of quartz and felspar in small grains, so 
Vol. hi.— r. 



that microscopic sections present between 
crossed nicols a characteristic mosaic structure. 
When a granitic rock becomes foliated, or its 
constituent minerals exhibit more or less 
elongation in definite directions, it is said to 
acquire a ' gneissoid ' structure, and may pass 
into a true gneiss. 

Granite occurs frequently in the form of in- 
trusive masses, which, while coarsely crystaUilie 
in the centre, may present a fine texture towards 
their margin. From the main mass, veins or 
apophyses are thrown oS into the neighbouring 
rocks ; and these veins, having cooled less 
slowly, are often fine-grained, and may pass 
into micro-granites and quartz-porphyries. It 
has been asserted that certain granites may have 
resulted from the extreme alteration of stratified 
rooks ; and hence geologists who hold this view 
recognise two types of granite, one igneous, and 
the other metamorphio. 

It is not uncommon to find in granite nod- 
ular masses which appear as dark patches on 
the fractured or polished surface of the rock. 
Whilst some of these inclusions seem to be 
fragments of foreign rook which have been 
caught up in the granitic magma and altered, 
others may be regarded as parts of the original 
magma differentiated during consolidation ; and 
it is notable that the inclusions are usually 
more basic than the matrix. (For comparative 
analyses of 1 he granite and its inclusions, v. 3. A. 
Phillips in Quart. Journ. Geol. Soo. 1880, 36, 1.) 

Granite is extensively employed for construc- 
tive purposes where massive work is required, 
as in the foundations of buildings, in docks, sea 
walls, the piers of bridges, and lighthouses. 
The specific gravity of granite is about 2-6 ; a 
cubic foot weighing about 166 lbs., and a cubic 
yard 2 tons. 

Granite rooks are always divided by joints, 
which usually run in three directions, thus 
splitting the rock into masses of roughly oub- 
oidal form. The stone is blasted in the quarry, 
and the blocks split up by ' plug and feather ' 
wedges. When the surface is required to be 
dressed smooth, it is ' fine-axed ' by continued 
tapping, at right angles to the face, with a 
special form of axe. Solid cylinders are turned 



GRANITE. 



on a lathe, and columns measuiing as much as 
8 feet in diameter may be thus wrought. The 
polishing of granite is efiected by means of cast- 
iron planes worked over the smooth surface, first 
with sand and water, and then with emery, the 
final polish being given with putty powder 
appUed on thick felt. In this way even elaborate 
mouldings may be readily polished. (For granite 
working, v. G. W. Muir, tfoum. Soo. Arts. 1866, 
14, 471 ; and G. P. Harris, Granite and our 
Granite Industries, London, 1888.) 

Granite rocks are extensively developed and 
quarried in Cornwall and Devon, where they 
occur as a series of bosses protruding through 
the kiUas oi clay-slate. The largest of these 
intrusions are, proceeding westwards, those of 
Dartmoor, Brown WiUy or St. Breward district, 
Hensbarrow or St. Austell, Cam Menelez or 
Penryn, and the Land's End oi Penzance dis- 
trict. In addition to these principal exposures 
there are numerous smaller masses. The granite 
of Devon and Cornwall is usually grey and 
coarse-grained, but red granite also occurs, as at 
lYowlesworthy in the western part of Dartmoor. 
A local variety, termed by R. N. Worth Trowhs- 
tcorthite, and described by Prof. Bonney, is 
composed of red felspar, with a tourmaline, purple 
fluorspar, and a little quartz. A handsome red 
granitic rock occurring near Luxullian, in Corn- 
wall, and hence called by Bonney I/uxuUianite, 
consists of red orthoclase, in large crystals, with 
schorl, 01 black tourmaline, and quartz. This 
is the rock of which the Duke of Wellington's 
sarcophagus, in St. Paul's, is formed. 

The nearest exposure of granite to London 
is at Mount Sorrel, in Leicestershire, where pink 
and grey biotite-granite, rather hornblendic, is 
worked for kerb-stones, paving setts, and road 
metal. The hornblende granites of the Channel 
Islands are quarried for similar purposes. Shap 
Fell, in Westmoreland, yields a beautiful biotite- 
granite, with large crystals of salmon-coloured 
orthoclase, which is now largely used as an 
ornamental material, and has been employed, 
for example, in the posts around St. Paul's. 
The granites of Scotland are of much industrial 
importance. Aberdeen granite was brought to 
London for paving in the 18th century, but the 
great development of the trade dates from about 
18S0. The Aberdeen stone, which is of grey or 
blue tint, is valued for monumental work ; 
the Peterhead granite is usually of a fine pink 
colour. The Ross of Mull, in Argyllshire, fur- 
nishes a handsome red granite, yielding blocks of 
exceptional size. Granite is also worked in 
Kirkcudbrightshire, where it occurs in bosses 
surrounded by slates ; the grey granite of Dal- 
beattie being well known in commerce. 

In Ireland, granite is very extensively de- 
veloped, the chief districts being in counties 
Wicklow, Galway, Mayo, Donegal, and Down. 
The largest quarries are those near Dalkey, 
which yielded the stone for Kingstown Harbour. 
The quarry near Castlewellan, Co. Down, which 
was opened to supply granite for the Albert 
Memorial, in Hyde Park, has since been closed. 
Granite is also found in the Isle of Man, Arran, 
Anglesea, Lundy I., and the ScUly Isles. 

It is needless to specify the numerous 
European localities in wluch granite is worked. 
Of late years a green ' granite ' (gabbro) from 
Warburg, in Sweden, has been imported as a 



monumental stone. In the United States, 
workings are established in a large number of 
localities, the granite-producing States being, 
in order of relative importance, Massachusetts, 
Maine, Rhode Island, Connecticut, Virginia, 
and New Hampshire. 

For a large collection of analyses of granites, 
V. J. Roth's Beitrage z. Fetrographie d. pluto- 
nische Gesteine (Berlin, 1873-84); H. S. 
Washington, U. S. Geol. Survey, Prof. Paper, 
No. 14, 1903 ; No. 28, 1904. F. W. R. 

GRANITE BLACK v. Azo- colottbino 

MATTERS. 

GRAPE. The berry of Vitis vinifera (Linn.). 
There are many varieties differing in size, shape, 
colour and composition. 

Konig gives as the average percentage 
composition — 

nitrogenous Free Invert Other carbo- 
Water substances acid sugar hydrates Fibre Ash 
79-1 0-7 0-7 150 1-9 2-1 0-5 

The sugar (glucose) in particular is liable to 
considerable variation, ranging from 9 to 18 oi 
19 p.c. 

This variation,' as well as that in the acidity 
— due to tartaric acid or acid potassium tar- 
trate — is influenced not only by the variety, 
but also by the cUmate and soil ; a wet winter 
and a hot, dry summer being generally favour- 
able to the production of sweet grapes, suitable 
for wine making, whilst much rain during 
the ripening period dilutes the juice and leads 
to the bursting and consequent injury of the 
berries. 

The proportion of skin and seeds shows con- 
siderable variation in different varieties, averag- 
ing about 2-2 p.c. of the whole fruit, and of this 
the seeds usually constitute about one-fourth. 
The skin contains tannin, and, according to 
Malvezin (Compt. rend. 1908, 147, 384), a yellow 
colouring matter, which, on oxidation either by 
exposure to air in aqueous solution, or by the 
action of an enzyme, present in red, but absent 
in white grapes, changes to a red substance. 

Sostegui (Gazz. chim. ital. 1902, 32, ii. 17) 
states that the red colouring matter is a tannin 
derived from protocatechuio acid and has the 
formula CeH3(0H)(jC0-CaH,(OH)0-C,H,(0H)j. 

The skin and seeds of grapes, in a moist con- 
dition, were analysed by Bailand (Rev. intern, 
falsif, 1900, 13, 92), who found them to have the 
following percentage composition : — 

Nitrogenous Soluble carljo-Cmde 

Water substances Fat hydrates fibre Ash 

Skin . 76-5 1-6 0-9 18-4 2-1 0-6 

Seeds . 38-7 5-5 8-6 18-9 27-6 0-7 

Wittmann found about 0-4 p.c. pentosans in 
grapes. 

The ash, according to Konig, contains — 
Per cent, of _ © „ o" « 

ash in dry O J « "S °- O " o" 
substance i? ^ gagpTglB 
Wholelruit 3-95 53'0 3-7 6-9 3-3 1-2 21-3 5-0 3-6 1-8 
SMn . 403 44-2 1-9 21-0 6-7 1-5 17-6 8-7 30 0-6 

Seeds . 281 28-7 — 33-9 8-6 0*6 24-0 2-5 I'l 3 

About 0-2 p.o. of manganese oxide is also 
usually present. 

Boric acid has been found in grapes (Cramp, 
ton, Amer. Chem. J. 11, 227; Baumert, Ber. 
21, 3290). Salicylic acid also occurs especially 
in the stalks (Mastbaum, Chem. Zeit. 1903 27 
829). ' 



GRAPHITE. 



Dried grapes constitute raisina and currants 
and are extensively used. Their average 
composition, as given by Konig, is respectively — 





Baisina 


Currants 


Water . 


. 24-5 


25-4 


Nitrogenous substances 


. 2-4 


1-2 


Fat ... 


. 0-6 


— 


Free acid 


. 1-2 


1-5 


Invert sugau . 


. 59-3 


61-8 


Cane sugar 


. 20 


— 


Other carbohydrates 


. 1-3 


6-9 


Crude fibre and seeds 


. 70 


2-4 


Ash . . . 


. 1-7 


1-8 



American analyses give considerably less 
water and more ash than these figures. 

H. I. 

6BAPE SEED OIL is obtained from grape 
seeds (Yiiis vinifera [Linn.]) by expression or 
by extraction. The oil is only of local import- 
ance, and is expressed only for local consump- 
tion. Thus, in Italy and in the south of France 
(and even in south Germany) it is said to be 
used as an edible oil. The cold expressed oil 
has a golden-yellow colour, and is free from 
odour. If the seeds have been stored for some 
time the expressed oil is dark, and acquires a 
slightly bitter flavour. The chemistry of this 
oil is not fully known, as the data obtained by 
the several observers who examined grape seed 
oil are very conflicting. At first tlus oil was 
credited with a very high acetyl value, and 
was compared in this respect with castor oil, so 
that its use for the manufacture of Turkey red 
oil had been proposed. More recent examina- 
tions have shown that grape-seed oil has a 
very high iodine value, so that accordingly 
the oil would seem to belong to the semi-drying 
or drying oils. A fresh examination of this oil 
is desirable in order to remove the doubts 
existing as to its composition. J. L. 

GRAPHIC TELLURIUM v. Telltoium. 

GrRAPHITE, a crystallised form of carbon, 
known also as plumbago, and popularly as 
black lead. It occurs usually in compact and 
crystalline masses, but occasionally in six- 
sided tabular crystals which cleave into flexible 
laminss parallel to the basal plane. The crystals 
were referred to the hexagonal system until A. E. 
von Nordenskiold, in 1855, after studying the 
crystals from Fargas, in Finland, declared them 
to be monoclinio. Kenngott, however, after- 
wards showed that they were truly rhombohedraJ 
(Pogg. Ann. 96, 110). 

Graphite is a mineral of iron-black or steel- 
grey colour, with metallic lustre, having a 
sp.gr. of 2-2. In consequence of its softness 
(H.=l) and the ease with which it produces a 
metallic streak when rubbed on paper, it is 
largely used in the manufacture of pencils, 
whence the name ' graphite ' given to it by 
Werner, from yfi^iD (I Write). It was formerly 
called molybdcena, and confused with molyb- 
denite (MoSj), a mineral which also gives a 
metallic mark on paper. (On the history of 
these names, and of plumbago, v. J. W. Evans, 
Trans. Philological Soo. 1908, 133.) Graphite 
seems to have been first recognised as a distinct 
mineral by Gesner, who figured a lead pencil in 
1565 (Roscoe). Soheele in 1779 showed that gra- 
phite was a kind of mineral carbon, since it could 
be converted into carbon dioxide by the action of 



nitric acid. As the carbon is usually associated 
with more or less iron, the older mineralogists 
described the mineral as a • carburet of iron,' 
but Vanuxem demonstrated that the iron is 
present as ferric oxide and not as a carbide. 
The ash left on the combustion of graphite 
usually contains, in addition to the ferric oxide, 
silica, alumina, and lime. 

Exposed on platinum foil to the flame of the 
blowpipe, graphite burns, but often with more 
difficulty than diamond. When heated with a 
mixture of potassium dichromate and sulphuric 
acid, it disappears. In order to obtain per- 
fectly pure graphite, the mineral is first ground 
and washed to remove earthy matter, and then 
treated, according to Bro^e's method, with 
potassium chlorate and sulphuric acid ; on sub- 
jecting the resulting product to a red heat, pure 
carbon is obtained in a remarkably fine state of 
division. 

The following analyses are selected from a 
large number by C. Mfene (Compt. rend. 64, 
1091) :— 



— 


I 


II 


in 


IV 


Carbon . 
Volatile matters 
Ash . 


91-55 
MO 
7-35 


81 '08 

7-30 

11-62 


79-40 

6-10 

15-50 


78-48 

1-82 

19-70 




10000 


100-00 


100-00 


100-00 



I. Very fine Cumberland graphite, sp.gr. 
2-345. II. Graphite from Passau, Bavaria, 
sp.gr. 2-303. III. Crystaillised graphite, from 
Ceylon, sp.gr. 2-350. IV. Graphite, from Buck- 
ingham, Canada, sp.gr. 2-286. 

Graphite when used for pencils is frequently 
mixed, in a powdered state, with pure clay, and 
the mixture consolidated by hydraulic pressure. 
It is also sometimes mixed with sulphur or 
with antimony sulphide. Brockedon first sug- 
gested the use of the hydraiilic press as a 
means of obtaining from powdered graphite a 
homogeneous and coherent mass, which could 
be readily sawn into pieces of convenient size. 
The finest pencil lead was yielded by the 
ancient mine at Borrowdale in Cumberland, 
where it occurred in pipes, strings, and irregular 
masses, or ' sops,' associated with a dyke of 
diorite and with intrusive masses of diabase, in 
the Cambro-Silurian volcanic series known as 
' the green slates and porphyries.' The Cum- 
berland graphite was formerly termed ' wad,' a 
name sometimes applied also to native oxide of 
manganese. (For description of the old Borrow- 
dale workings v. J. C. Ward in Geol. Survey 
Mem. on Lake District, 1876.) A small amount 
of graphite, about 100 tons per annum, is 
obtained from the Craigman mine, near Cumnock 
in Ayrshire ; here the mineral usually exhibits 
a columnar structure, and it has been produced 
by the baking action of dykes of igneous rock 
on seams of coal. 

Excellent graphite is found in Siberia, espe- 
cially at the Mariinoskoi mine, in the Tunkinsk 
Mountains, Government of Irkutsk. This de- 
posit, discovered in 1838, occurs in gneiss, asso- 
ciated with diorite ; it has been largely 
worked by M. Alibert to supply Faber's pencil 
factory. In 1860 graphite was discovered in 
granite near the river Nisohne Tungusska, and 



GRAPHITE. 



workings were undertaken by M. Siderov. (For 
Russian graphite v. N. Koksharov, Materialien 
z. Mineralogie Kusslanda, 1862, 4, 153, where 
analyses are given.) 

The best quality of graphite found in large 
quantities is that from Ceylon. The mineral 
is widely distributed through the western and 
north-western provinces of the island, and is 
obtained from a large number of small pita, 
there being but few mines of any size. The 
output amounts to about 30,000 tons per annum, 
with a value of rather over half a million pounds 
sterling. (On the graphite deposits of Ceylon 
V. A. K. Coomaraswamy, Mineralogioal Survey 
of Ceylon, 1903, etc. ; Quart. J. Geol. Soc. 
1900, 56, 590.) In India, graphite is found at 
several localities, chiefly in the Madras Presi- 
dency, the best coming from Travancore, but 
even this is far inferior to that from Qeylon. 

In the United States, graphite is widely 
diffused, but rardy in sufficient quantity to be 
worked. The principal locality is Ticonderoga, 
in Essex Co., New York, where the Dixon 
Crucible Co. have worked a schist containing 
about 10 p.o. of graphite. It has also been 
worked to a limited extent near Raleigh, North 
Carolina ; at Stourbridge, Mass. ; at Cumber- 
land HUl in Rhode I. ; and at Sonora in Cali- 
fornia. The graphite ' ores ' are crushed or 
stamped, and then washed, whereby the flakes 
of graphite are readily separated from the denser 
matrix. In the Laurentian gneiss of Canada, 
graphite is of frbquent occurrence, and has 
occasionally been worked, as at the Buckingham 
Mines. The mineral is usually found in veins 
and nodular masses, or finely disseminated 
" through bands of limestone. 

In Europe, extensive deposits of graphitic 
schists occur in the Eastern Alps and in the 
mountainous region between Bohemia and 
Bavaria (Bohmerwald). These are extensively 
mined in Austria (in Moravia, Styria, and 
particularly in the east of Bohemia), where the 
annual output reaches 50,000 tons; but the 
material is of inferior quality, containing often 
50 p.c. of ash. Considerable amounts are also 
obtained in the north of Italy, but the well- 
known locality at Passau in' Bavaria is now 
little worked. (On Alpine Occurrences of 
Graphite v. B. Weinschenk, Abh. bayer. Akad. 
Wiss. 1898, 19, 609, 521 ; 1901, 21, 279.) 

Daubree has obtained graphite artificially 
by decomposing carbon disulphide in contact 
with metallic iron at a high temperature; 
while H. Sainte-Claire Deville prepared it by 
passing vapour of carbon tetrachloride over 
fused cast iron. Crystalline graphite is often 
formed in blast furnace slag during iron smelt- 
ing, and is known to workmen as kish ; and it is 
present in grey pig iron. Considerable quantities 
of graphite are now produced commercially, 
together with carborundufli, in the electric 
furnace. The artificial production of graphite 
(as well as various properties of the natural 
mineral) is dealt with by H. Moissan (The 
Electric Furnace, London, 1904). Graphite 
also occurs in certain meteoric irons, such as 
that of Toluca in Mexico. A cubic form of 
graphitic carbon, discovered in a meteoric iron 
from Youndegin, Western Australia, has been 
described by Fletchen under the name of 
Clijtonite (Min. Mag. 1887, 7, 121). 



In consequence of its refractory character, 
graphite is largely used in the manufacture of 
crucibles, retorts, twyers, and other objects re- 
quired to withstand high temperatures. For 
crucibles, the powdered mineral is mixed with 
Stourbridge fire-clay, and made into a paste 
with water ; the kneaded mass is allowed to lie 
for many weeks before the,cruoible is moulded ; 
the vessel when moulded is slowly dried, and 
carefully fired in a seggar. 

As a lubricating agent graphite is highly 
valued, since it diminishes friction and tends to 
keep the moving surfaces cool. To obtain the 
best results the powdered mineral should be 
carefully selected and sized. For steam cylin- 
ders it is used dry; for heavy bearings it is 
mixed with grease ; and for light bearings with 
oil. Made into a paint with linseed oil, it has 
been advantageously employed as a coating for 
metal work. Graphite is also used dry for 
polishing stoves and other objects of cast iron, 
the thin flakes forming a lustrous coating which 
protects the metal. Blasting powder and heavy 
ordnance powders are likewise glazed with 
graphite, for though it slightly diminishes the 
explosive force of the powder it protects it from 
damp. Being a good conductor of electricity, 
graphite is used in electrotyping, as originally 
suggested by Murray ; the moulds upon which 
the metal is to be deposited receiving a conduct- 
ing surface by being coated with finely divided 
graphite. 

E. Donath, Dei Graphit, eine chemisch- 
technische Monographic, Leipzig and Wien, 
1904 ; Graphite, its Occurrence and Uses, Bull. 
Imp. Inst. London, 1906, 4, 353 ; 1907, 5, 70 ; 
F. Cirkel, Graphite, its Properties, Occurrence, 
Refining, and Uses, Dept. of Mines, Ottawa, 
1907 ; A. Haenig, Der Graphit, eine technische 
Monographic, Wien and Leipzig, 1910. 

L. J. S. 

GRASSES. The term ' grass ' is used by the 
agriculturist to denote, not only plants which 
belong to the graminece, but also other pasture 
or meadow plants, or even certain weeds 
common on cultivated land. 

The true grasses are characterised by a 
somewhat low content of nitrogenous substances 
and by the richness of the ash in silica and its 
poverty in lime and magnesia, whilst clovers 
and other leguminous crops possess the exactly 
opposite features. H. I. 

GREASES. The term ' grease ' was applied 
originally to all kinds of fats having a buttery 
consistence. At present, however, the term 
' grease ' is restricted to low - class material, 
chiefly obtained from waste products, such as 
kitchen grease, ship's grease, tripe tallow^ 
slaughter-house grease (' tankage ' grease), 
bone grease, skin grease, greases from carcase- 
rendering establishments, and garbage fats. All 
these greases must be looked upon as varieties 
and (or) mixtures of lard, tallow, bone fat, 
horse fat, fish stearines, &c. 

Greases are characterised by a dark colour, 
by a high percentage of free fatty acids, 
and a correspondingly high proportion of 
unsaponifiable matter. They are also charac- 
terised by an objectionable odour. 

Black grease is the dark, almost black, fatty 
matter which is recovered from cotton seed 
mucilage, on decomposing the latter with 



GUAIACOL. 



mineral acids {sec Coitob Seed Oil). This black 
grease is used in the manufacture of low-class 
candle materials, after a purification by distilla- 
tion with superheated steam, and further 
treating the distillate in the same manner as 
the fatty acids of the candle industry are 
worked up (see Saponification). J. L. 

GREEN EBONY. Green ebony is a yellow 
dyewood formerly employed to some extent in 
this country, but now almost entirely replaced 
by other colouring matters. It is a native of 
Jamaica oi West India, and is obtained from 
the Excaecaria glandulosa (Siv.) or Jacaranda 
ovalifolia (R. Br.). The trunk of the tree is 
about 6 inches in diameter; the wood is very 
hard, and of an orange-brown colour when 
freshly but and stains the hands yellow. Eefer- 
ences to this dyestufE are meagre, and it 
does not appear to have been ever largely 
employed. Bancroft (Philosophy of Permanent 
Colours, 1813, ii. 106) states that green 
ebony contains a species of colouring matter 
■ very similar to that of CUoropJiora tinctoria 
(Gaudich) (old fustic), apd is sometimes employed 
in its stead ; and 0. NeiU (Dictionary of Calico 
Printing and Dyeing, 1862) mentions that it is 
used in dyeing greens and other compound 
shades. Until recently it had a limited sale 
in Yorkshire as a dye for leather, but appears 
to have entirely passed out of use as a wooUen 
dyestuff. It is little used in silk dyeing, but 
was formerly employed for greening blacks. 

Green ebony contains two crystalline colour- 
ing matters, which are distinguished by the fact 
that whereas one, excceoarin, is Hot precipitated 
by lead acetate solution, the second, jacarandin, 
is completely deposited by this reagent (Perkin 
and Briggs, Chem. Soo. Trans. 1902, 81, 210). 

Exeoeearin C13H12O5 crystallises in lemon- 
yeUow needles, sparingly soluble in cold alcohol, 
and molting with effervescence at 219°-221°. 
It is soluble in aqueous and alcoholic alkaline 
solutions with a violet-red colouration, and these 
liquids, on exposure to air, are rapidly oxidised, 
and assume a brown tint. 

Exeoeearin does not dye mordanted fabrics, 
but is a substantive dyestuff in that it has a 
weak but decided affinity for the animal fibres 
with which it gives, preferably in the presence of 
tartaric or oxalic acid, yellow shades. Benzoyl- 
exeoeearin C,3Ha05(C,H50)3, colourless needles, 
m.p. 168°-171°; and exccecarindimethyl ether 
Ci3H,„9j(CH,)2 yellow needles, m.p. H7°-119°. 
On fusion with alkali exeoeearin gives hydro- 
quinonscarboxylie acid (CO^H : OH : 0H= 1:2:5) 
and a substance melting at 124°, which is 
probably hydrotoluquinone 

(CH3:0H:0H=1:2:5). 

By the action of bromine upon a solution of 
exeoeearin in alcoholic potassium acetate excce- 
carone CisHjoOj, flat copper coloured needles 
or leaflets, melting at about 250°, is produced, 
and this by the action of sulphurous acid is 
readily converted into exco3carin. With alco- 
holic quinone solution exeoeearin gives the 
compound CjHjOj'CisHjsOg, minute green- 
coloured leaflets, melting with decomposition at 
190°, and from this sulphurous acid also regener- 
ates exeoeearin. From these results it appears 
evident that exeoeearin contains free hydro- 
quinone hydroxyls. 

Jacarandin C^ «Hi ,05, yellow plates or leaflets. 



m.pi 243°-24;5°, dissolves sparingly in alcohol 
and the usual solvents to form pale yellow 
liquids having a green fluorescence. With 
caustic alkali solutions it gives orange-red 
liquids ; with alcoholic lead acetate a bright 
orange coloured precipitate ; and with alcoholic 
ferric chloride a dark greenish-black solution. 
It dyes mordanted woollen fabrics the following 



Chromium Aluminium Tin Iron 

Dull yellow- Orange-brown Bright golden Deep 

brown yellow olive 

Acetyl jacarandin CijH]„Oj(CjH30)2, pale- 
yeUow needles, melts at 192°-] 94°, and when 
digested with boiling alcoholic potassium acetate 
gives the salt (CuHiaOs-CuHjiOjJK, yellow 
needles. Benzoyljacardndin C,iHjo05(C,H50)2 
forms yellow prismatic needles, m.p. 167°-169°. 

As indicated by Bancroft (I.e.) the colours 
given by green ebony are similail in oharactei 
to those yielded by old fustic. Employing 
mordanted woollen cloth the following shades are 
produced : — 

Chromium Aluminium Tin Copper Iron 

Dull yellow- Dull brown- Golden Pale brown Olive 

brown yellow yellow green 

With 40 p.c. of the dyewood the iron mordant 
gives greener and brighter shades than with 
larger amounts, in which case a browner colour 
is produced. Possibly from this green shade, 
and the extremely hard and compact nature of 
the wood, the name ' green ebony ' has originated. 

A. G. P. 

GREEN ALIZARIN v. Madder. 

GREEN CINNABAR. A mixture of chrome 
yellow and Prussian blue. 

GREEN EARTH, Terre verte, v. Pioments. 

GREEN, EMERALD, v. Chbomium. 

GREEN, GUIGNET'S. v. Chbomium. 

GREEN SMALT, Cobalt green, v. Pigments. 

GREEN ULTRAMARINE, Chromium sesqui-. 
oxide, V. Chromium. 

GREEN VITRIOL, Ferrous sulphate, v. Iron. 

GREENLAND SPAR v. Cryolite. 

GREENOCKITE, Cadmium sulphide, v. Cad- 
mium. 

GRENAT BROWN v. j«o-Pubpubic acid. 

GREY ANTIMONY ORE, Antimony sulphide, 
V. Antimony. 

6RI-SHI-BU-ICHI. Japanese name for an 
alloy of copper and silver of a rich grey colour. 

GRISOUTINE. An explosive consisting of 
a mixture of nitroglycerin, nitrocellulose, 
ammonium nitrate, and kieselguhr. 

GROSSULARITE v. Garnet. 

GUACAMPHOL, GUAIACETIN, GUAIA- 
FORM, G0AIAKINOL, GUAIAMAR, GUAIASA- 
NOL, GUATANNIN v. Synthetic drugs. 

GUAIACENE v. Quaiacum, art. Resins. 

GUAIACIC ACID v. Quaiacum, art. Resins. 

GUAIACOL {Monomethoxycatechol) 
OHCeHi-OMe 
is a constituent of guaiaoum resin (Herzig and 
Schiff, Monatsh. 1898, 19, 95), and occurs in 
beechwood tar from which it can be separated 
by treating the fraction of the tar that comes 
over at 200°-205° with ammonia to remove 
acids ; it is then again fractionated, and the 
lower boiling fraction is dissolved in ether and 
treated with potassium hydroxide. The potas- 
sium salt of guaiacol is filtered, washed with 
ether, and recrystaUised from alcohol, after 



6 



GDAIACOL. 



which it Is decomposed with sulphuric acid, 
and the guaiaool redistilled. (For other 
methods of separation, c/. D. R. PP. 
87971, 56003, 100418, Chem. Zentr. 1899, 
i. 764.) Guaiacol is prepared from o-anisidine. 
500 grams o-aniddine are diazotised, and the 
solution of the diazo salt is then poured into a 
boiling solution of 600 grams of copper sulphate 
in 600 c.c. of water. The guaiacol is then 
separated by distillation in steam (D. R. P. 
167211 ; Prdl. 1905-7, 128 ; cf. also D. R. P. 
95339 ; J. Soe. C!hem. Ind. 1898, 269, 314). 

Pure guaiacol can be obtained by dissolving 
catechol (55 parts) in ethyl' alcohol (2000 parts) 
and adding nitrosomonomethyl urea. The 
mixture is cooled to 0° and 20 parts of sodium 
hydroxide dissolved in a small quantity of 
water is added, drop by drop, with constant 
stirring. The solution is filtered, the alcohol 
distilled off, and the residue is fractionated in 
vacu6 CD. R. P. 189843 ; Frdl. 1905-7, 1151). 

Guaiacol is also prepared by heating an 
equimolecnlar mixture of catechol, potash and 
potassium methyl sulphate in tightly closed 
vessels at 170°-180°, or by heating catechol and 
methyl iodide in methyl alcohol. Thompson 
(Eng. Pat. 5284, 1893) suggests the purification 
of guaiaool by treatment with a freezing mixture. 
Guaiacol has a characteristic odour and 
crystallises in long vitreous transparent prisms, 
which appear rose-red in sunlight ; m.p. 28-5°, 
b.p. 202-47738 mm. (Freyss, Chem. Zeit. 1894, 
18, 665); sp.gr. 1-140 at 25°. When quite 
pure it is non-caustic and non-poisonous (Be'hal 
and Choay, Compt. rend. 1893, 116, 197; 
Kupriauow, J. Soc. Chem. Ind. 1895, 57). 
It is soluble in most organic solvents, and 
to a less extent in water. With a trace of ferric 
chloride its alcoholic solution gives a blue 
colour, which becomes emerald-green on the 
addition of more ferric chloride. Guaiacol also 
gives a blue colour with traces of hydrogen 
peroxide (Denigfes, J. Pharm. 1909, 31). 

Guaiacol is employed in pharmacy as an 
expectorant and intestinal antiseptic ; also in 
pulmonary tuberculosis in cases of typhoid and 
other fevers, and for the relief of superficial 
neuralgia. 

Kuprianow (Centralbl. f. Bakteriol. 1894, 15, 
933, 981) has suggested the use of pure guaiacol 
in the internal treatment of cholera, since he 
found that a solution of 1 in 500 of tliis reagent 
completely prevents the development of the 
cholera baciUus. 

Guaiacol should be preserved in amber- 
coloured bottles protected from the hght, and 
should only be used in pharmacy when quite 
pure. 

Tesia. — (\) 2 c.c. of guaiacol mixed with 
4 c.c. of light petroleum, should separate at 
once into 2 layers. (2) 1 c.c. of guaiacol should 
dissolve in 2 c.c. of N. sodium hydroxide when 
heated ; on cooling the mixture should congeal 
to a white saline mass, which gives a clear 
solution with 20 o.c. of water. (3) 1 c.c. of 
guaiacol treated with 10 c.c. of N. sulphuric acid 
should give a pure yellow colour. For other 
tests, V. Marfori, J. Soc. Chem. Ind. 1891, 487 ; 
Fonzea Diacon, Bull. Soc. chim. 1898, 19, 191 • 
Gu^rin, J. Pharm. Chim. 1903, [vii.] 17, 173. ' 
Guaiacol can be estimated approximately 
by conversion into catechol, by heating with 



water in a current of hydrobromic acid; or 
0-5 gram of the guaiacol is dissolved in a little 
water, 10 c.c. of alcohol added, and the solution 
made up to 1000 cc, and 20 c.c. of this solution 
are mixed in a test-tube with 1 c.c. of sodium 
nitrite solution (1 : 100), and 1 cc. dilute nitric 
acid (1 : 200). A characteristic red-brown colour 
is produced, which is compared within about 
10 minutes with the colourations given by 
suitable standard solutions (Adrian, Zeitsch. 
anal. Chem. 1901, 40, 624). 

Guaiacol, when treated with hydrogen 
cyanide, in the presence of sodium or zinc 
chloride, yields vanillin (Roesler, D. R. P. 
189037; Frdl. 1905-7, 1280; Guyot and Gry, 
Compt. rend. 1909, 149, 928 ; Bull. Soc. chim. 
1910 [iv.] 7, 902). 

Ouaiacol vnonosvlphonic acids can be obtained 
by treating guaiacol with sulphuric acid at 
30°-60°, the ortho- and para- acids formed 
being separated by converting them into the 
basic salts of the alkaline earths', or of the 
heavy metals, the ortho- salts being readily 
soluble in water, whereas the para- salts are 
insoluble or sparingly soluble. By the action 
of sulphuretted hydrogen, or some suitable acid, 
the salts are then converted into their respective 
acids CD. R. P. 188506; Frdl. 1905-7, 936; 
D. R. P. 132607 ; Frdl. 1900-02, 1113 ; Hahle, 
J. pr. Chem. 1902, [ii.] 65, 95: Lamiere and 
Perrin, Bull. Soc. chim. 1903 [iii.l 29, 1228- 
Rising, Ber. 1906, 39, 3685 ; Paul, ibid. 2773, 
4093 ; Ginhorn, Fr. Pat. 391601, 1908 ; J. Soc. 
Chem. Ind. 1908, 1176; Andrfe, J. Pharm. 
Chim. 1898, 7, 324). 

The most striking difference between the 
ortho- and the para- acids is their action with 
calcium or barium chloride, with which the para- 
acid yields a white precipitate, whereas the 
ortho- remains unchanged. With nitric acid the 
para- acid forms yellow dinitroguaiacol (m.p. 
122°), whilst the ortho- acid merely gives a 
dark-red colouration. It is important that 
when the ortho- acid is used therapeutically, it 
should be free from the para- compound, as the 
latter gives rise to secondary reactions (Ellis, 
J. Soc. Chem. Ind. 1906, 335). 

The alkali guaiacol sulphonates are employed 
as drugs (Alpers, U.S. Pat. 69258j!; J. Soc. 
Chem. Ind. 1902, 364). TagUavini has pre- 
pared salts of the sulphonates with antipyretic 
and analgesic bases (BoU. Chim. farm. 1909. 
48, 6). 

Carbonyl chloride condenses with the alkali 
guaiacol sulphonates in alkaline solutions, giving 
derivatives such as potassium carboruUodiguaiacol 
disvZphonate C0[0C,Hj(0Me)S05K]j, and patas- 
Slum carbonatodiguaitKol sulphonale 

C,H,(OMe)OCOjC,H,(OMe)SO,K 
(Einhorn, D. R. P. 203754, 1909). 

Guaiacol S-sulphonic acid is obtained by 
sulphonating an acetyl derivative of guaiacol 
with or without the addition of dehydrating 
agents, the resulting acetyl guaiaool sulphonio 
acid IS hydrolysed, neutralised, and the resultmg 
acid IS isolated as such, or in the form of its 

??,o^?- ^i ^- ^^^^^^; J- ^°''- Chem. Ind. 1909, 
1UU5). Ihe corresponding carbonate 

(MeO-0eHjSO,H)2CO3 

is formed by treating guaiacol carbonate with 

sulphuric acid in the cold until the product is 



GUAIACOL. 



soluble in water. It melts at IIS'-IIT", with 
evolution of carbon dioxide (D. R. P. 216060 ; 
J. Soo. Chem. Ind. 1909, 1223). 
, Triphenyl guanidine guaiacol sulplionate is 
obtained by the action of tiiphenyl guanidine 
sulphate on barium guaiacol sulphonate; It 
crystallises in leaflets, m.p. 60°, and can be 
Used as a local ansesthetic (Goldschmidt, Chem. 
Zeit. 1901, 25, 628). 

A number of important compounds of o- 
guaiacol sulphonic acids with alkaloids are 
described by Schaefer (J. Soc. Chem. Ind. 1910, 
928). They are used in medicine and are also 
of scientific interest. The alkaloid salts are 
prepared by neutralising the guaiacol sulphonic 
acid w^h the required alkaloid, and purifying 
the product by filtration and recrystallisation, 
or the amorphous salt is obtained by evapora- 
tion at low temperature or in vacii6. The salts 
may also be obtained by double decomposition 
between a soluble alkaloid, and a readily 
soluble salt of the acid in molecular proportions, 
using alcohol, wafer, &c., as a solvent. Most 
of the alkaloid salts are non-crystalline or 
crystallise with difficulty. The most important 
of the salts described by Schaefer are : 

QuinxTie guaiacol bisulphonate (guaiaquin) 
[CsH3(OH)(OMe)S03H]2,C,„H2jNa02 is ayeUow- 
ish crystalline powder, soluble in water, alcohol, 
and (filute acids. The solution is coloured blue 
by a drop of ferric chloride solution. It softens 
at about 80°, and becomes liquid at 130°. 

Codeine-o-guaiacol svlphonate 

C,H,(OH)(OMe)SO,H,C, sH^iNO,, 
m.p. 164°-165°, is a well-crystallised neutral 
salt. It is readily soluble in hot water and in 
alcohol, but almost insoluble in ether and 
chloroform. It gives the characteristic blue 
colouration of o-guaiacol sulphonic acid with 
ferric chloride, and when its aqueous solution is 
treated with an alkali, codeine is precipitated. 
Other opium and cinchona compounds, as well 
as compounds with strychnine, brucine, atropine, 
hyoscine, hyoscyamine, and cocaine, are de- 
scribed. 

Guaiacol iron and lithium sulphonates have 
been prepared (Schaefer, Eng. Pat. 21747, 1899). 

Ouaiahinol, quinine derivative of hromo-guaia- 
col, Cs„Hj4NjOj,2HBr,C8H,(OH)(OMe), forms 
fine crystalline yellow scales, readily soluble in 
water. It is said to be practically non-toxic, 
and its aqueous or alcoholic solution is readily 
absorbed by the skin (Pharm. J. 1901, 66, 132 ; 
Schaefer, Eng. Pat. 8227, 1897). 

Chwiamphol, the camphoric acid ester of 
guaiacol C8Hn(CO-OOeH4-OMe)2, obtained by 
the action of camphoric acid chloride on sodium 
derivative of guaiacol. Forms white, odourless, 
tasteless needles, and has been recommended for 
the relief of night sweats in phthisis. 

Cfuaiacol lienzoate (benzosol, benzoyl guaiacol) 
CeH.-CO-OCeH«-OMe is prepared by heating an 
alcoholic solution of potassium derivative of 
guaiacol with the requisite amount of benzoyl 
cjiloride, and purifying the substance by crystal- 
lisation from alcohol. It is a colourless, odour- 
less, tasteless powder, almost insoluble in water, 
readily soluble in organic solvents. It has m.p. 
66°, and is used in the treatment of pulmonary 
tuberculosis (Eng. Pat. 6366, 1890; J. Soo. 
Chem. Ind. 1891, 383; Walzer, Chem. Zeit. 
Rep. 1891, IS, 165). 



Guaiacol cinnamale (styracol, cinnamyl 
guaiacol) CsH/CO-OCgHj-OMe is formed by the 
interaction of molecular weights of guaiacol and 
cinnamyl chloride. It forms colourless needle- 
shaped crystals, m.p. 130°, which are employed 
in catarrhal affections of the digestive tracts, 
and in the treatment of phthisis. 

Guaiacol combines with tannin and cinnamio 
acid to form a compound which is said to be of 
use in medicine. It melts above 300°, is insoluble 
in most organic solvents, and dissolvesjn alkalis 
and also in pyridine, from which the pyridine 
derivative crystallises in weE-shaped rhombic 
needles (D. R. P. 133299 ; Frdl. Nissel. 1900-02, 
1111). 

Guaiacol valerate C^Hj-CO-OCsHj-OMe, a 
yellowish oily liquid, b.p. 246°-265°, is used in 
medicine under the name of geosote (Rieck, 
J. Soc. Chem. Ind. 1897, 632). It is prepared 
by the action of valeryl chloride on sodium 
derivative of guaiacol. 

Cfuaiacol salicylate (guaiacol salol) 
C„Hi(0H)C0 0CeH4-0Me 
is a white crystalline, odourless, tasteless 
powder ; m.p. 65°. It is formed by the action 
of phosphorus oxyohloride on a mixture of 
sodium guaiacol salicylate, and is used as an 
intestinal antiseptic. 

Guaiacol succinate C2Hi(CO-OC5Hi-OMe)2 is 
formed by the action of phosphorus oxyohloride 
on a mixture of guaiacol and succinic acid in 
molecular proportions. It forms fine silken 
crystalline needles ; m.p. 136°. 

Guaiamar, the glyceryl ether of guaiacol 
C8H4(OMe)OCaH,02, is formed by the action of 
anhydrous glycerol on guaicol. It is a white 
crystalline body, m.p. 75°, soluble in water and 
in most organic solvents. It has a bitter 
aromatic taste, and is employed in medicine as 
an antiseptic for internal and external applica- 
tion (J. Soc. Chem. Ind. 1900, 371 ; 1902, 1346). 

Guaiasanol (diethylglycocollguaiaool hydro- 
chloride) MeO,CjHjO-CO-CHjNEtj,Hei, m.p. 
184°, is non-poisonous, and said to possess slight 
ansesthetic, antiseptic, and deodorising proper- 
ties (Einhorn, Chem. Zeit. Rep. 1900, 24, 33 ; 
J. Soo. Chem. Ind. 1900, 464). By the action 
of the monochloracetio esters of phenols with 
secondary amines of the fatty series, many 
compounds, similar to the above, have been 
prepared (Einhorn and Heinz, Arch. Pharm. 
240 [8] 631 ; D. R. P. 105346). They are non- 
poisonous, odourless, and ^strongly antiseptic 
substances. 

Quaiaperol (piperidine derivative of- guaiacol) 
is prepared by dissolving 85 parts of piperidine 
and 248 parts of guaiacol in benzene or light 
petroleum, and allowing the solution to evapo- 
rate (Tunniclifie, Chem. Soc. Trans. 1898, 145). 

Valuable albuminous products said to be 
applicable in medicine for tuberculous and other 
cases are obtained by the interaction of guaiacol 
with egg or other albumin in aqueous or alcoholic 
solution (D. R. P. 162656; Erdl. 1905-7, 931). 

Guaiacol, when treated with ethoxyacetyl 
chloride, bromide, or iodide, reacts thus : 
MeO -OeH vO|H+a|COCH jOEt 

-^MeOOaHiCOOCHjOEt. 
The product is a. colourless, odourless oil ; 
b.p. 150°/10 mm. The corresponding methoxy 
derivative boils at 170°-171°/10 mm., and has 



8 



GUAIACOL. 



very similar properties to the ethoxy derivative. 
Both substances are non-poisonous, and can be 
used therapeutioaEy as external remedies 
(D. E. P. 171790 ; Frdl. 1905-7, 933). 

Ouaiaform (geoform) is produced by the 
condensation of guaiacol (2 mols. ) with formalde- 
hyde (1 mol.). It is a tasteless, yellow, non- 
irritant and non-toxic powder, but on keeping 
it acquires the vanilla flavour. It is insoluble 
in water, but readily soluble in ether, benzene, 
or alcohol (Ehlert, Pharm. J. 1902, 68, 61). 

„ . , I . OMeCeHiOv^ _,„ . 

Ouaiacol carionate oMeC H O,^ "^ ^^^' 

pared by passing phosgene into a solution of 
guaiacol in sodium hydroxide. The substance is 
filtered off, washed with sodium hydroxide solu- 
tion, and recrystaUised from alcohol. It is a white 
crystalline powder, m.p. 84°-87°, of neutral 
reaction, and almost odourless and tasteless, 
soluble in most organic solvents, but insoluble 
in water. Its alcoholic solution yields no 
characteristic colour with ferric chloride. When 
taken internally its action is very similar to that 
of guaiacol, but it is less liable to derange the 
stomach. It is employed as an expectorant in 
the treatment of tuberculosis and bronchitis, 
and also as an intestinal antiseptic in the 
treatment of typhoid fever and intestinal 
indigestion (D. R. PP. 99057, 58129, 117346, of 
1901 ; D. R. P. 224160 ; Einhorn, Chem. Zentr. 
1910, ii. 618). 

Quaiacol cMorocarhonate is a colourless oil ; 
b.p. H2°/25 mm. It is prepared by the inter- 
action of antipyrine, carbonyl chloride and 
guaiacol (D. R. P. 117624 of 1901 ; Einhorn, 
D. R. P. 224108, 1910 ; Chem. Zentr. 1910, ii. 
517). 

Ouaiaeolcarhoxylic acid C,'H.a{0'E){0Ma)C02'B. 
is formed by the action of carbon dioxide on 
sodium derivative of guaiacol, previously heated ; 
the product is heated for some time, and is then 
acidified with hydrochloric acid, the free acid 
being recrystaUised from water or dilute alcohol. 
It is a white, odourless crystalline powder ; 
m.p. 148°-150°. It has a bitter taste, is readily 
soluble in hot water, and its aqueous solution 
is coloured blue by ferric chloride. The acid 
and its salts have been recorqmended as anti- 
septics and antirheumatics (Pharm. J. 1890, 
977). 

Guaiacol, when oxidised with laccase, yidds 
0(C,H3-OMe)aO 
telraguaiacoqmTwne | | .afinecrystal- 

0(CeH3-OMe)jO 
line powder, m.p. 135°-140°, having a purplish- 
red colour with a faint green metallic lustre. It 
is insoluble in water, but gives mahogany-red 
solutions with chloroftirm and with acetic acid. 
It also forms coloured solutions in alkalis (Ber- 
trand, Compt. rend. 1903, 137, 1269). 

Dimethylamino e-guaiacylamyl ether, the corre- 
sponding piperido derivative and the piperido- 
7-guaiaoyl-propyl ether are formed by the inter- 
action of a halogen hydrocarbon alkyl ether of 
guaiacol with a secondary amine, thus : 
a!(0H2)„O-R+NHMe/=Me2N(CHii)„OR ; on 
a:{CHj)„0-R-MraC5Hi„=C6HioN(CHi,)„0-R 
(where a:=halogen). They are employed in 
medicine as ansesthetics (D. R. P. 184986 ; 
Frdl. 1905-7, 1050). 

Hexamethylenetetraminetriguaiacol oij8ta31iseB 



in brilliant needles, which become scft at 80°, 
and melt to a turbid liquid at about 95°. When 
distilled in steam it yields guaiacol (Eng. Pat. 
24072, 1908 ; J. Soo. Chem. Ind. 1909, 490). 

Chloroacetyl guaiacol OMeCsHiO-CO-CHjCl is 
prepared by treating a mixture of guaiacol 
monochloroacetic acid and pyridine with phos- 
phorus oxychloride. It forms white needles, 
m.p. 58°-60° (Einhorn and Hentz, I.e.). 

Guaiacol chloroformic ester is a colourless oil ; 
b.p. 112°/25 mm. (D. R. P. 117624; Frdl. 
1900 02, 1165). 

Benzyl guaiacol is a yellow, beautifully 
fluorescent oil ; b.p. 269°-270°/430 mm. (Bosco- 
grande, Chem. Zentr. 1898, i. 207). 

Guaiacol picrate forms orange-red needles; 
m.p. 80°. Many other guaiacol derivatives have 
been prepared, some of which have been recom- 
mended for use in medicine (Eng. Pat. 5856, 
1894; Ruhemann, Chem. Soo. Trans. 1902,421; 
D. R. P. 120558; Frdl. 1900-02, 1112; D. R. P. 
157355 ; Frdl. 1902-04, 616; Knapp and Suter, 
Chem. Zentr. 1904, i. 391 ; Moureu and Lazennec, 
Compt.. rend. 1906, 142, 894; BischofE, Ber. 
1906, 39, 3846; Gattermann, Annalen, 1907, 
357, 313 ; Foumeau, J. Pharm. Chim. 1910, [vii.] 
1, 55, 97 ; Manchot, Ber. 1910, 43, 949 ; Wohl 
and Berthold, ibid. 2175 ; Hoffmann, D. R. P. 
255924 ; Chem. Zentr. 1910, ii. 1105). 

A number of azo derivatives of guaiaoo^ are 
described by Leonardi (Atti R. Accad. Lincei. 
1907 [v.] 16, ii. 639); some nitro and amino 
derivatives by Reverdin and Crepieux, Ber. 
1903, 36, 2257; 1906, 39, 4232; Paul, ibid. 
2773 ; KulJing, ibid. 1905, 38, 3007 ; Fiehter 
and Schwab, ibid. 1906, 39, 3339). 

Thiogiiaiacol and thioguaiacol xantJiate have 
been prepared by Mauthner (Ber. 1906, 39, 
1347). 

Guaiacol forms mono-, di-, tri-, and tetra- 
halogen derivatives (Cousin, Compt. rend. 1898. 
127, 759 ; Tassily and Lerride, ibid. 1907, 144, 
757 ; BuU. Soc. chim. 1908, [iv.] 3, 124 ; Mameli, 
Gazz. chim. ital. 1907, 37, ii. 366 ; Robertson, 
Chem. Soo. Trans. 1908, 791). The iodo 
derivatives are said to be applicable to medicine 
(Mameli and Pinna, Chem. Zentr. 1907, ii. 2044). 

Guaiacol phosphite, m.p. 75-5°, is a white 
crystalline powder, with a piquant non-caustic 
taste and slight odour, soluble in most organic 
solvents, but only sparingly in water (BoUard, 
D. R. P. 95578 ; J. Soc. Chem. Ind. 1897, 632 ; 
Ellis, Eng. Pat. 27527, 1896). Its medicinal 
properties are similar to those of guaiacol. 

Another guaiacol phosphite, m.p. 59°, is 
described by Dupuis (Compt. rend. 1910, 150, 
622). 

Guaiacol phosphate (C^HjOMe),?©, is pre- 
pared by the interaction of phosphorus oxy- 
chloride and sodium derivative of guaiacol. It 
forms colourless crystals; m.p. 98°, insoluble in 
water and alcohol, but soluble in ether, chloro- 
form, and acetone. It is used as an intestinal 
antiseptic and in hectic fever. 

A number of other phosphorus compounds 
of guaiacol are described by Auger and Dupuis 
(Compt. rend. 1908, 146, 1151), and by Bupuis 
(ibid. 1910, 150, 622). 

Gvaiacol-cacodylatt AsMejOa-CjH^OMe, is a 
white hygroscopic, crystalline, very unstable 
salt (Astruc and Murco, J. Pharm. Chim. 12, 553). 

GUAIACONE V. Guaiacum, art. Resins. 



GUANIDINE. 



9 



CUAIACONIC ACID v. Quaiacum, act. B]!:sI^'S. 

GUAIACUM V. Eesins. 

GUAIENE V. Quaiacum, ait. Besins. 

ClUAIOL V. Quaiacum, art. Eesins. 

GDANIDINE HN : C(NHj)j occurs in small 
quantities in etiolated vetch seedlings, 3 
kilos, of dried material yielding 1 gram of the 
nitrate (Schulze, Ber. 1892, 25, 658) ; and in 
beet juice (Lippmann, ibid. 1896, 29, 2651)^ 

Guanidine was first prepared by Streoker 
(Aimalen, 1861, 118, 159) by oxidising guanine 
with potassium chlorate and hydrochloric acid; 
and it is obtained in small quantity by oiddising 
egg albumen with potassium permanganate, or 
gelatin with barium or calcium permanganate 
(Lossen, J. Pharm. Chim. [iii.] 31, 32 ; Kutscher 
and Kickgraf, Sitzungaber. K. Akad. Wiss. 
Berlin, 1903, 28, 624) ; it is formed synthetically 
(1) by heating biuret and hydrogen chloride at 
160''-170° (Finckh, Annalen, 1862, 124, 332) ; (2) 
from chloropicrin and alcoholic ammonia at 
100° (Hofmann, Ber. 1868, 1, 145); (3) from 
ethyl orthocarbonate and aqueous ammonia at 
150° (Hofmann, .Vnnalen, 1866, 139, 111) ; (4) 
from carbonyl chloride and ammonia (Bouchardt, 
Zeitsch. Chem. 1870, 58) ; (5) from ammonium 
chloride and alcoholic cyanamide at 100° (Erlen- 
meyer, Annalen, 1868, 146, 259); (6) from 
cyanogen iodide and alcoholic ammonia at 100° 
(Bannow, Ber. 1871, 4, 161) ; (7) by the action 
of aqua regia on dicyanodiamide, when a quan- 
titatiye yield of the nitrate is obtained (Ulpiani, 
D. R. P. 209431). 

Guanidine is usually prepared by heating 
ammonium thiooyanatefor 20 hoursat 180°-190°, 
treating the fused mass with water and allow- 
. ing the guanidine thiocyanate to crystallise 
from the solution ; it is then purified by animal 
charcoal and reorystaUised from alcohol and 
water. The thiocyanate is converted into the 
carbonate by treating the concentrated aqueous 
solution with one equivalent of potassium car- 
bonate, the solution is evaporated and the 
residue extracted with hot alcohol in which the 
guanidine carbonate is insoluble, and this is 
afterwards recrystallised from water (Delitsch, 
J. pr. Chem. 187], [ii.l 9, 2 ; Volhard, ibirl 15). 
According to Goldberg, Siepermann, and Hem- 
ming p. R. P. 1898, «7820), a better yield of 
guanidine salts is obtained when the ammonium 
thiocyanate is mixed with wood charcoal and 
the oxide or salt of a heavy metal, and the 
mixture heated in a current of ammonia, 

(1) 2NHjCNS-|-ZnO 

=CH5Ns,HCNS+ZnS+H20 ; 

(2) 2NH,CNS-|-ZnO+Pba2 

=2NH3+2GH5N3,Ha+ZnS+PbS+HjO ; 
or guanidine thiocyanate can be prepared by 
heating the thiocyanate of a heavy metal under 
pressure in an atmosphere of ammonia at 180° 

Pb(CNS)a-f2NH3=PbS+CH5Nj,HCNS. 

Guanidine is a deliquescent crystalline solid, 
readily soluble in alcohol or water ; it is volatile 
and strongly alkaline, absorbs carbon dioxide 
from the air and forms crystalline salts. The 
thermal value of the basic function of guanidine 
is +32-1 Cal., intermediate between that of 
barium hydroxide -f31-7 Cal. and sodium 
hydroxide +36-4 Cal. (Matignon, Compt. rend. 
1892, 114, 1432). Guanidine is decomposed into 
ammonia and urea on boiling with baryta water 



or dilute sulphuric acid (Osaikowsky, Bull. Soc. 
chim. 1872, [ii.] 18, 161 ; Baumann, Ber. 1873, 
6, 1376) ; and is completely decomposed into 
carbon dioxide and ammonia by heating with 
concentrated acids or alkalis. Guanidine is 
decomposed, evolving two-thirds of its nitrogen, 
when mixed with sodium hypochlorite or hypo- - 
bromite (Fenton, Chem. Soc. Trans. 1879, 14). 

When the hydrochloride is heated at 180°, 
ammonia is evolved and higiianide is formed, the 
reaction being similaB to the formation of biuret 
from urea : 
2HN : CCNHj) 

=NH3-f HN : C(NHj)NH'C(NHa)NH. 

In its physiological action, guanidine is 
highly toxic ; doses smaller than poisonous ones 
are in rabbits excreted unchanged in the urine 
(Pommerrenig, Beitr. Chem. Physiol. Path. 
1902, i. 561) ; it acts on frog's muscles, pro- 
ducing spontaneous twitching and affecting 
theii contractility, and it is supposed that 
the guanidine acts by combining with two 
different substances in the muscle, one of which 
is responsible for the twitching, and the other 
for the changes in contractility (Camis, J. physiol. 
1909, 39, 73). Although guanidine does not 
appear to be a normal oxidation product of 
arginine in the body (Pommerrenig, I.e.), it is 
found among the products of pancreatic auto- 
digestion (Kutscher and Otori, Zeitsch. physiol. 
Chem. 1904, 43, 93). Small quantities of 
guanidine, O'l per thousand, are injurious to 
chlorophyllous plants, whilst fungi utilise it as 
a source of nitrogen but not of carbon (Kawa- 
kita, Bull. Coll. Agr. Tokyo, 1904, 6, 181). 

Many salts of guanidine give a yellowish- 
white flocculent precipitate with Nessler's re- 
agent, which can thus be used as a test for small 
quantities of the salts of the base, a 0-05 p.c. 
aqueous solution of guanidine nitrate gives a 
bulky precipitate and a 0-01 p.c. solution is 
rendered turbid (Schulze, Ber. 1892, 25, 661). 
Another test for guanidine is the development of 
a deep yellow to orance red colouration with 
alkali hypochlorites (de Coninck, Compt. rend. 
1898, 126, 142). Guanidine is usually estimated 
as the picrate, the salt being collected on a 
Gooch asbestos filter, dried at 110° and weighed 
(Vozarik, Zeitsch. angew. Chem. 1902, 16, 670) ; 
or it can be converted into the strongly alkaline 
carbonate and titrated with standard acid 
(Grossmann and Schiick, Chem. Zeit. 1906, 30, 
1205). 

Guanidine forms crystalline salts with mineral 
and with organic acids ; it also forms charac- 
teristic double salts. The hydrochloride 

CH5N3,HC1 
forms double salts with mercuric chloride 

CH5N3,HCl,2HgCl2 
(Byk, J. pr. Chem. [ii.] 20, 233)-; with gold 
chloride CB5N3,HC],AuCla, deep yellow, spar- 
ingly soluble needles (Hofmann, Ber. 1868, 1, 
146) ; with platinic chloride (CH6N3,Ha)2,PtCl4, 
yellow needles, soluble in water, sparingly so in 
alcohol (Strecker, Annalen, 1861, 118, 160). The 
nitrate, CH5N3,HN03, crystallises in large plates, 
m.p. 214°, 10-76 parts dissolve in 100 parts of 
water at 15-9°. The compound with silver 
nitrate 0H5N3,AgNO3 crystallises in needles. 
The nitrite CHbNj.HNOz forms glittering 
prisms, m.p. 76°-78-5° (Lossen, Annalen, 1891, 



10 



GUANIDINE. 



265, 129). The svlpTuae (CH5Ns)8.H:iiSO, crys- 
talliaes in the regular system and is soluble in 
water (Bodewig, J. 1876, 763) ; it forms a double 
salt mth aluminium avlphate 

(CHsN8)j,H,S04,Alj(S04)3,12H,0 
crystallising in large, well-developed hexagonal 
■ prisms belonging to the soalenohedral class of 
the rhombohedral system, and having sp.gr. 
1 -806 at 13-5° (Ferraboschi, Proo. Camb. Phil. Soe. 
1908, 14, 471). The carbonate (CH5N8)2,H2C03 
forms octahedral or tetragonal prisms ; sp.gr. 
l-238-l-251-(Sohr5der, Ber. 1880, 13, 1072). 
The metaphosphate CH5N3,HPO, forms a fine 
crystalline precipitate (Pohl, Zeitsch. physiol. 
Chem. 1889, 13, 296). The percJiromate 

- (CH5N3),CrO„H,0 

forms small brownish-yeEow, double-refracting 
prisms, and yields the usual blue solution with 
ether and dilute sulphuric acid (Hofmann and 
Buchner, Ber. 1909, 42, 2773). The thiocyanate 
CH5Na,H0NS has m.p. 118°, and 100 parts of 
water dissolve 73 parts at 0°, or 134-9 parts at 
15° (Engel, Bull. Soc. chim. 1885, 44, 424). The 
platinothiocyanate (CH5N8)a,HjPt(CNS), forms 
beautiful red crystals that blaclten at 170°-175° 
(Guareschi, Chem. Zentr. 1891, u. 620). The 
cyanurate (CH5Na)3,(CNHO)3 forms silky needles 
(Bamberger, Ber. 1887, 20, 71). The dioxalate 
0H5N3,C.H,04,H20 is sparingly soluble (Streo- 
ker, Z.C.). The picrate CH3N„C,H2(NOj)30H 
is a sparingly soluble, yeUow, crystalline salt, 
1 part dissolves in 2630 parts of water at 9°, and 
it does not melt at 280° (Emich, Monatsh. 1891, 
12, 24). According to von Cordier (Chem. 
Zentr. 1906, i. 340), guanidine picrate exhibits 
stereoisomerism. The salt, as usually prepared, 
forms dark yeUow plates that, owing to repeated 
twinning, have a hook-like structure, but when 
guanidine prepared by decomposing methyl- 
guanidine sulphate with barium hydroxide is 
used, the picrate crystallises in rosettes of bright 
yellow needles. The two forms are identical in 
composition, sp.gr., temperature of decomposi- 
tion and electric conductivity, but differ in 
colour, crystalline form and solubility, 100 parts 
of water dissolve 0'037 parts of the plates at 0°, 
0-061 at 20°, and 0-574 at 80°. The solubility of 
the needles is 0-043, 0-060, 0-800 at these tem- 
peratures respectively. One form cannot be 
converted into the other by crystallisation, and 
the author suggests that they are stereoiso- 
merides, the plates being the stable modification, 
NHj-C-NHj-CjHjOjNa, and the needles the labile 

NH 
NHg-C-NHj-CsHaOjNa". The lenzenesvlphmate 

HN 
has m.p. 200°, the p-toluene-svlphonate, m.p. 
206°, and the a- and p-rMpMhaleneavlpJuynaiea, 
m.p. 257° (Remsen and Garner, Amer. Chem. J. 
1901, 25, 173). The i-nitroacetylanlliranilate 
has m.p. 247° (oorr.) (Bogert and Klaber, J. 
Amer. Chem. Soc. 1908, 30, 807). The acetate 
CH5N,-C2H408 forms shining needles, m.p. 
229-230° (Ostrogovioh, Gazz. chim. ital. 1897, 
27, i. 223). The picrohnate CBLNa-CioHgOsN, 
Is soluble in alcohol (Schenck, Zeitsch. physiol. 
Chem. 1905, 44, 427). 

Guanamlnes. When the guanidine salts of 
the first seven of the fatty acid series are heated 
at 220°-230°, water and ammonia are eliminated 



and heterocyolib bases called guattaminea are 
formed : these are well characterised orystaUine 
compounds. Formoguanamine 

HC^".C(NH8)/^ 
melts and decomposes at a high temperature ; 
acetguanamine CHa-C^lcl^^j^N melts at 

265°: propionoguanamine blackens at 300°; 
mnarlihoguanamine melts at 130° (Nencki, Ber. 
1874, 7, 1584 ; Haaf, J. pr. Chem. 1891, [p.] 43, 
75) 

"cMoroguanidlne CHiClNa, obtained by the 
action of bleaching powder solution on guamdine 
carbonate in ice water, forms a pale yellow 
crystalline powder that decomposes at 150 
(Kamenski, Ber. 1«78, 11, 1602). 

Bromoguanidine CHiBrNj, formed from 
equimolecular proportions of bromine and guam- 
dine carbonate, crystallises in yellpw needles. 
By the action of 3 mols. bromine on 1 mol. 
guanidine carbonate, the compound 

.CHsNa-HBr-Brj 
is formed, crystallising in dark red prisms. The 
corresponding iodine compound CHjNj^HI-Ij 
crystallises in prisms the ooloni of iodine 
(Kamenski, I.e.). 

Nitroguanidine NH : C(NHj)NH-N02 was 
first prepared by Jousselin (Compt. rend. 1877, 
85, 548; 1879, 88, 814, 1086) by the action of 
fuming nitric acid and nitric oxide on guanidine 
nitrate, and called by him nitrosoguanidine. 
Pellizzari (Gazz. chim. ital. 1891, 21, ii. 405) 
showed that it was the nitro compound, and his 
results were confirmed by Thiele (Annalen, 1892, 
270, 1), who also prepared it by the action of 
fuming nitric acid and sulphuric acid on guam- 
dine thiocyanate. It crystallises from water in 
colourless needles, melts and decomposes at 
230° with evolution of ammonia ; it dissolves in 
372-375 parts of water at 19-3°, oi in 11 parts of 
boiling water. The heat of combustion at con- 
stant pressure is -1-210-3 Cal. and the heat of 
formation from its elements is -f 22 Cal. (Matig- 
non, Compt. rend. 1892, 114, 1432). The saver 
derivative CHaN^OjAg is colourless and almost 
insoluble in water ; the nitrate CH^OjNj-HNO, 
is crystalline and melts at 147° ; the hydro- 
chloride CHjOjNj.HCl crystallises in plates or 
prisms. 

Nitiosoguanidlne NH : C(NHa)NH-NO is ob- 
tained by the partial reduction of nitroguanidine 
with zinc dust and sulphuric acid. It forms 
yellow needles, explodes violently at 160''-165°, 
is soluble in alkalis and reprecipitated by carbon 
dioxide ; it also gives the Liebermann reaction. 
The alkali solutions give a beautiful purple 
colouration with ferrous salts. The silver salt 
CHaON4Ag is a colourless explomve precipitate ; 
the copper salt (CH30N4)2Cu is reddish brown, 
and the niehd salt (CHaON4)]Ni is vermilion 
red (Thiele, Annalen, 1893, 273, 133). Accord- 
ing to Hantzsoh, Schiimann, Engler (Ber. 1899, 
32, 575, 1703), nitrosoguanidine is a true nitros- 
amine and its constitution is represented by the 
formula NH : C(NHa)NH-NO, since it has a 
neutral reaction, yields mainly nitrous acid and 
not nitrogen when decomposed by acids, and 
does not interact with phosphorus pentachloride 
or acetyl chloride. On the other hand, Whiteley 
(Chem. Soc. Trans. 1903, 31) and Tsekugaefl 



QUANrDINE. 



II 



(Ber. 1906, 39, 3383) consider that the coloured 
metallic derivatives are salts of the tautomeric 
diazo-hydrate form HN : C(NH,)N : N-OH. 

Aminoguanidine HN : C(2SrH2)NHNHj,is ob- 
tained by reducing nitroguanidine with zinc 
dust and acetic acid at 40° until a test portion 
develops no colouration with ferrous sulphate 
and an alkali (Thiele, Annolen, 1892, 270, 23). 
The mixture is filtered, the filtrate evaporated 
till it is only feebly acid, and the aminoguanidine 
bicarbonate precipitated in the cold by adding 
a concentrated solution of alkali bicarbonate 
(D. R. P. 59241). Also prepared by heating 
an alcohoUo solution of hydrazinehydrochloride, 
and cyanamide in a reflux apparatus (Pellizzari 
and Cnneo, Gazz. chim. ital. 1894, 24, i. 450). 
A yield of 81 p.c. of the theoretical is 
obtained by the electrolytic reduction of the 
nitro compound, suspended in water slightly 
acidified with sulphuric acid, using a tin cathode 
and a current density of 250 amperes per square 
metre and a temperature of 10° (Boehringer and 
Sohne, D. R. P. 167637). 

Aminoguanidine is crystalline, soluble in 
water or alcohol, decomposes on boiling with 
dilute acids or alkalis, yielding first semicarba- 
zide and finally ammonia, carbon dioxide, and 
hydrazine (Curtius, Ber. 1896, 29, 769). Amino- 
guanidine forms crystalline salts with mineral 
acids : the hydrochloride CH|5!N4,HG1 forms large 
prisms, m.p. 163° ; the double salt with platinic 
chloride (CH,N4,HCl)2,PtC!l4 is a yellow precipi- 
tate, m.p. 145°-146° ; the nitrate CHjNi.HNOa 
forms large shining plates, m.p. 144° ; 100 parts 
of water dissolve 12-01 parts at 16-9° ; the 
sulphate (CH,N4)2,HjS04,H20 crystallises in 
needles, m.p. 207°-208° j the hisulptiate 

CH,N4,Hi,S04 
crystaUises in large plates, m.p. 161° ; the 
picrate CHeN4,C,H,0,ll3 is precipitated as 
yellow needles from hot water. The copper 
compounds Ca{CSiNi)i,2SN03 and 

Cu(CH5N4)i„Hi,S04 
are violet crystalline precipitates ; the hi- 
carbonate CHeN4,HjCOs (Thiele, Annalen, 1898, 
302, 332) melts at 172° and is almost insoluble 
in cold water. 

Acelaminoguanidine CB[5N4(C2H30) forms a 
crystalline nitrate, m.p. 85°-90° and picrate; 
fcrrmylaminoguanidine nitrate 

KN0s,H2NC(NH)NH-NHCH0 
melts at 143°, the picrate melts at 193° ; oxalyl- 
aminoguanidine HN : C<NH2)NH-NH-C0-C0jH 
melts at 231°-232° (Thiele and Manohot, Anna- 
len, 1898, 303, 37). 

Aminoguanidine and its alkyl and aryl 
derivatives contain the grouping — NH-NHj, 
present in hydrazines, and semioarbazide, and 
like them readily form condensation products 
with aldehydes, ketones, sugars, and ketonio 
acids ; these are usually well characterised 
crystalline compounds, forming crystalline salts 
with mineral and organic acids. For the con- 
densation products with aldehyde, chloraldehyde, 
chloral, v. Thiele and DraUe (Annalen, 1898, 
302, 278); with benzaldehyde, v. Thiele (ibid. 
1892, 270, 1), Wedekind (Ber. 1897, 30, 444) ; 
with diaoetyl, acetylaoetone, acetonylacetone, 
V Thiele and Dralle (I.e.) ; with galactose, 
glucose, and lactose, v. Wolfi (Ber. 1895, 28, 
2613); with glyoxylio acid, v. Thiele and 



DraUe {I.e.), Doebner and Gartner (Annalen, 
1901, 315, i); with pyruvic acid, v. Wedekind 
and Bronstein {ibid. 1899, 307, 297). For the 
preparation and properties of aliyl and aryl 
substituted derivatives of aminoguanidine, v. 
Pellizzari and Cuneo (Gazz. chim. ital. 1894, 24, 
i. 450), Pellizzari and Rickards {ibid. 1901, 31, 
i. 526). 

Diaminoguanidine HN : C(NH-NH2)2 does 
not exist in the free state ; its hydrobromide 
CHjNj.HBr is formed by the action of cyanogen 
bromide (1 mol.) on hydrazine (2 mols.) ; it 
crystallises in plates, m.p. 167°; the picrate, 
CH,N5,CeH,0,Nj, melts at 191°; the hydro- 
chloride at 185° ; the platinochloride at 172°-173° ; 
all the salts reduce FehUng solution and ammo- 
niacal silver nitrate solution. Dibenzylidenedi- 
aminoguanidine HN : C(NH-N : CHPh)^ yellow 
crystals, m.p. 180° ; the hydrobromide melts at 
243°, and the hydrochloride at 230° (Pellizzari 
and Cantoni, Gazz. chim. ital. 1905, 36, 'i. 291). 

Dihydroxyguanidine hydrobromide 
HN : C(NH-OH)j,HBr 
is formed by the interaction of cyanogen bromide 
and hydroxylamine in methyl alcohol and ether 
at —20° ; it forms colourless, flat, hygroscopic 
needles that decompose at 96° (Wieland, Ber. 
1905, 38, 1445). 

Mefhylguanidine HN : C(NH2)NHMe has 
been isolated from extract of muscle (Gulewitsch, 
Zeitsch. physiol. Chem. 1906, 47, 471), and is 
prepared by boiling creatine with mercuric or 
lead oxide and dilute sulphuric acid (Dessaignes, 
Annalen, 1854, 92, 407 ; 1856, 97, 340). It can 
be synthesised from methylamine hydrochloride 
and cyanamide (Erlenmeyer, Ber. 1870, 3, 896). 
It is a strongly alkaline, volatile, crystalline sub- 
stance, and liberates ammonia and methylamine 
on heating with potassium hydroxide. The 
aurichloride 02H,Ns,HCl,Aua, melts at 198°- 
200°; the platinichloride (C2H,N3,Ha)2,Pta4 
melts at 194°-195° (Schenck, Arch. Pharm. 1909, 
247, 466). The oxalaie (C2H,N4)2,C2H204,2H20 
is crystalline and soluble in water. The picrate 
crystallises from water in two distinct jnodifica- 
tions (Gulewitsch, I.e.). The picrolonate 

C2H,N,,C.„H,05N4 
melts at 291° (Wheeler and Jamieson, J. Biol. 
Chem. 1908, 4, 111). 

For other alkyl and aryl substituted deriva- 
tives of guanidine, some of which have thera- 
peutic properties, v. Strakosch (Ber. 1872, 5, 
692); Tatarinow (J. 1879, 401); Noah (Ber. 
1890, 23, 2196); Hofmann {ibid. 1869, 2, 601) ; 
Fischer {ibid. 1897, 30, 2414);' Alway and Vail 
(Amer. Chem. J. 1902, 28, 168) ; Kampf (Ber. 
1904, 37, 1681); Keidel (D. R. PP. 1892, 66650; 
1898, 104361). 

Guanidine forms condensation products with 
dicarboxylic acids (Traube, Ber. 1893, 26, 2551 ; 
Ruheman and Stapleton, Chem. Soc. Trans. 1900, 
805 ; Kaess and Gruszkiewicz, Ber. 1902, 35, 3600); 
with p-ketonic acids (Jaeger, Annalen, 1891, 262, 
365) ; with p-diketones (Evans, J. pr. Chem. 
1892, 45, 489; Wense, Ber. 1886, 19, 761); 
with mahnonitrile (Merck, D. R. PP. 165692, 
166693) ; with ethyl cyanacetaie (Traube, D. R. P. 
1900, 115253). 

Guanidine forms compounds with sugars 
containing 3 mols. of sugar and 1 mol. of guani- 
dine : these exhibit mutarotation and have a 



12 



GUANIDINE. 



lower optical activity than the sugars from 
which they are derived (Morrell and Bellars, 
Chem. Soo. Trans. 1907, 1010). M. A. W. 
GUANINE, 2-amino-Q-oxy purine, 
NH— CO 

HjNO C-NH\ 
II II i^CH 

N CN^ 

was discovered by Uiiger in guano in 1844 
(Annalen, 51, 395 ; 58, 18 ; 59, 58), and though' 
Hoppe-Seyler failed to find it in the excrement 
of fowls and geese, Haeter obtained it from the 
excrement of a heron (Ardea cinerea) fed on fish 
and flesh (Med. Chem. Untersuch. 1871, 582) ; 
WiU and Gorup Besanez found it in the excre- 
ment of a spider, in the organ of Bojanus of the 
mussel, and in the green gland of the crayfish 
{cp. Weinland, Zeit. Biol. 25, 390) ; -and Pecile 
found 0-0008 gram of guanine per litre in the 
urine of a pig fed on bran, and in an unhealthy 
condition (Annalen, 1876, 183, 141). In addi- 
tion to its occurrence among the excretory 
products of the animal, guanine is fairly widely 
distributed throughout the tissues ; thus it 
occurs, together with hypoxanthine, in the 
protamine from salmon roe, forming 6-8 p.c. of 
the ripe organ (Piooard, Ber. 1874, 7, 1714) ; it 
occurs in the pancreas, spleen, liver, and muscle 
of the ox, in quantities varying from 0-020 to 
0-746 p.c. (Braginsky, Zeitsch. physiol. Chem. 
18S3, 8, 395 ; Kossel, ibid. 404 ; Schindler, ibid. 
1889, 13, 432) ; and it is found in the skin of 
fishes (Ewald and Kruckenberg, Chem. Zentr. 
1883, 705). Gu anine is widely spread throughout 
the vegetable kingdom, Schutzenberger found 
it, together with other purine bases, in yeast 
extract (Compt. rend. 1874, 78 ; Chem. Zentr. 
1877, 73) ; Schulze and Bosshard isolated it, 
together with hypoxanthine and xanthine, from 
young potato tubers, sugar beet, leaf buds of 
plane and maple, bark of plane, from lupins, red 
clover, vetch, young grass, and oats (Zeitsch. 
physiol. Chem. 1884, 9, 420) ; and v. Lippmann 
obtained it from beet juice (Ber. 1896, 29, 2645). 
According to Levene and Mandel (Biochem. 
Zeitsch. 1908, 10, 215) guanine is one of the 
cleavage products of nucleic acid, when the 
hydrolysis is effected by acetic acid in the 
presence of lead acetate at 150°. 

Guanine exists in guano partly as the 
calcium compound, partly in substances like 
nuclein, from these it is lij&erated by boiling for 
4 hours with dilute sulphuric acid, the liquid is 
cooled and filtered, and the filtrate made 
alkaline with sodium hydroxide and again 
filtered. The guanine and uric acid are pre- 
cipitated in the filtrate by the addition of 
ammoniacal silver solution, the precipitate 
washed with cold and hot water, and then 
decomposed by hot dilute hydrochloric acid, the 
silver chloride filtered off, the filtrate decolorised 
with animal charcoal, and the guanine pre- 
cipitated by ammonia, a small quantity of urea 
in hot nitric acid is added, and the mixture set 
aside to crystallise. The guanine nitrate now 
free from uric acid is dissolved in dilute sodium 
hydroxide and the guanine precipitated by the 
addition of ammonium chloride, this last opera- 
tion removing the xanthine (Wulff, Zeitsch. 
physiol. Chem. 1893, 17, 468). 

Fischer (Ber. 1897, 30, 559) has shown that 



guanine is 2-amino-6-oxypurine from the fact 
that imino-ifi-uric acid 
NH-CO^ 
H-CO^ 



HN: 



<3l 



>CH-NH-CO-NHj 



obtained synthetically by Traube (Ber. 1893, 
26, 2551) from guanidine and ethylmalonate, 
yields, on treatment -svith hydrochloric acid 
(sp.er. 1-19), at 120°, the same 2-am,ino-6 : 8- 

/NH-COC-NH\ 
dioxypurine NHj-Cl || /CO as ia 

NSN CNH/ 

obtained from Iromogtianine C5H4BrON5 (Fischer 
and Reese, Annalen, 1883, 221, 342) by the 
action of hydrochloric acid at 130°. Further, 
a synthetic guanine. Identical in every way with 
the natural product, is -obtained when 6-oxy- 
2 : S-dichloropvrine is heated with alcoholic 
ammonia, and the resulting chloroguanine 
reduced by means of hydriodio acid (Fischer, 
Ber. 1897, 30, 2226). The synthetical produc- 
tion of guanine has also been effected by Traube 
(Ber. 1900, 33, 1371) from 2 : i-diamino-6- 

hydroxy-pyrimidine HaN-CsT -jT.p/jjjj L^^' 

obtained by the condensation of guanidme and 
ethyl cyanoacetate in the presence of sodium" 
ethoxide. The nitroso derivative of this com- 
pound yields, on reduction with ammonium 
sulphide, 2:4: 5-iriamino-6-hydroxypyrimidine, 
wliich, when heated with an equivalent amount 
of sodium formate and 8-10 times its weight of 
anhydrous formic acid, is converted into guanine. 
A similar synthetic production of guanine from 
2-cyanamino-4:-ami7io-6-hydroxypyrimidine 

obtained by the condensation of dieyanodia- 
mide and ethyl cyanoacetate in the presence of 
sodium ethoxide, forms the subject of certain 
patents of Merck (D. R. PP. 1905, 158591, 
162336). 

Guanine is an amorphous powder, insoluble 
in water, alcohol, or ether, but soluble in 
acids or alkalis, forming salts of a di-acid base, 
or dibasic acid respectively. It can be obtained 
in the form of small rhombic crystals when the 
freshly precipitated compound is dissolved in a 
large excess of ammonia at 30°-35°, and the 
filtered solution allowed to evaporate slowly 
(Drechsel, J. pr. Chem. 1881, 24, 44); or in 
crystals resembling those of creatinine zino 
chloride, when a warm dilute alkaline solution 
(1 : 2000) is mixed with about one-third its 
volume of alcohol, acidified with acetic acid and 
allowed to cool (Horbaozewski, Zeitsch. physiol. 
Chem. 1897, 23, 226). 

The administration of guanine as food to 
rabbits produces neither increase in purine 
excretion nor pathological changes in the 
kidney • but subcutaneous or intravenous injec- 
tions of guanine dissolved in caustic soda, cause 
a great increase of purine substances, especially 
uric acid, in the urine (Schittenhelm, Chem. 
Zentr. 1902, i. 1306 ; Schittenhelm and Bendix, 
Zeitsch. physiol. Chem. 1905, 43, 365). 

Guanine is converted to the extent of 
60-70 p.c. into xanthine when heated with 
excess of 25 p.c. hydrochloric acid for 32 hours 
(Fischer, Ber. 1910, 43, 805); and undergoes 
profound decompositwn, yielding ammonia, 
carbon dioxide, formic acid, and glycocoll on 



GUARANA. 



13 



prolonged treatment with concentrated hydro- 
chloric acid at 180°-200° (Wnlff, Zeitsoh. 
phydol. Chem. 1893, 17, 468). A micro-organism 
belonging to the class of coccus bacteria and 
found in the excrement of pigeons, flourishes in 
a culture containing guanine, which is decom- 
posed into urea, guanidine, and carbon dioxide 
(Ulpiani and Cingolani, Atti. R. Accad. Lincei, 
1905, [v.] 14, ii. 596). 

The following derivatiyes of guanine have 
been described : — 

Salts. (1) With iases, the sodium 
NajOCsHsNjO.eHjO; 
barium CsHaNsOBa ; and copper 

CsHsKjO-CuaO and C5H5N5CUO ■ 

deriva-tives. (2) With acids, the hydrochloride 
CsHjNjO.HCl.HjO, forms double salts with zinc, 
cadmium, mercury, or platinic chloride ; hydro- 
hromide C5H5N50,HBi,2JH20 ; hydriodide 

C5H5NsO,HI,2JH20 
formsa double salt with bismuth iodide ; nitrates 
. C,HsN.O,HN03,lJH20 ; 

C5H5N50,2HN03,2HjO ; 
3CsH5N50,4HN03,4HaO ; 
and 3C5H5N50,5HN03,5iHaO ; 
sulphate (C5H5N50)2HjS04,2H20 ; oxalate 
3C5H5NBO,2C2Ha04 ; tartrate, 

dichromate CbHjNjO.HjOjO, ; picrate 

C.H^NsO.CsHaNaOj.HaO; 
picrolonate C5H|;ONj,2C]oHg05N4; ferricyanide 
(C5H5N50)„H3re(CN)8,8H20 ; niiroferricyanide 
(C5HsN50)2H2(CN)5NOre,liH20 ; metaphos- 
phate C5H|iN50,HP03,a;HjO. (3) With salts, 
mercuric chloride C5H5N50,HgCl2,2JH20 ; silver 
nitrate C5H5N50,AgN03, the silver picrate 
compound CjHjAgNjO.CjHjNjOjlJHjO is in- 
soluble in cold water. {Cp. Vagei, I.e. ; Streoker, 
Annalen, 118, 152; Bailee, J. pr. Chem. [ii.] 
47, 539 ; Neubauer and Ketner, Annalen, 103, 
268 ; Wulff, Zeitsch. physiol. Chem. 1893, 17, 
468 J Levene, Biochem. Zeitsch. 1907, 4, 320). 
Acyl derivatives. Acetylguanine 

is crystalline, sparingly soluble in water, alcohol, 
or ether, and may be heated at 260° without 
change. Propionylguanine C5H40N5(C8H50) is 
crystalline, and remains unchanged when heated 
at 260°, Benzoylguanine 



CjH.ONjCOjH.O) 
is also crystalline {cp, also Bayer & Co., D. R. P. 
213711). 

Azo derivatives. Guanine and other purine 
bases that are not substituted in position 7 
react with diazobenzenesulphonio acid to form 
coloured azo compounds, in which the -N : NR 
group is attached to carbon atom 8. Guanine 
and p-dichlorodiazobenzene chloride yield a 
dark-red dye, which forms S-aminoguanine when 
reduced. The amino compound does not itself 
couple with diazo compounds, but can be 
diazotised at 40°, and then yields a violet dye 
with an alkaline solution of R salt (Burian, Ber. 
1904, 37, 696, 708; Hans Fischer, Zeitsch. 
physiol. Chem. 1909, 60, 69). This reaction has 
been applied by Amatore de Giacomo (Zeitsch. 
wiss. Mikrosoop. 1910, 27, 267) to a micro- 



chemical method for demonstrating the presence 
of guanine in the renal system of birds. 

Bromoguanine CjHjNjOBr is a white crystal- 
line powder, almost insoluble in water, alcohol, 
or ether. It forms crystalline salts with acids, 
e.g. CsIIjNjOBr.HCl, and also unites with lead 
or silver to form crystalline compounds, which, 
when heated with methyl iodide at 100°, yield 
bromocafieine. Nitrous acid converts bromo- 
guanine into bromoxanthine (Fischer and Reese, 
Annalen, 1883, 221, 336). 

NH-CHj-C-NHV 

Deoxyguanine \ 11 ^CH is 

H5N-C=N — C-N-^ 
obtained when guanine is eleotrolytically re- 
duced in 60 p.c. sulphuric! acid solution, it 
crystallises in microscopic needles, melts and 
decomposes at 204°, and has strongly basic 
properties combining with atmospheric carbon 
dioxide. It is oxidised by bromine to 2-amino- 
N:CH-C-NH\ 



purine 



1. 



^CH a crystalline 



H2N-C=N-C-N^ 
base more readily soluble than its isomeride, 
adenine. 

Tests. Warm dilute solutions of guanine 
hydroohloiide give with a saturated solution of 
picric acid, an orange red crystalline insoluble 
precipitate ; xanthine and hypoxanthine give 
a similar reaction in very concentrated solutions 
only (St. Carpranioa, Zeitsch. physiol. Chem. 
1880, 4, 233). 

When guanine nitrate solution is evaporated 
it leaves a yellow residue, soluble in potassium 
hydroxide with a yeUow colouration. On 
evaporating the yellow solution to dryness, it 
affords first a purple, then a violet colouration, 
and on exposure to air the original colour returns 
(Briicke, Montash. 1886, 7, 617). 

Estimation. The formation of the insoluble 
picrate has been recommended by WulH 
(Zeitsch. physiol. Chem. 17, 468) for the estima- 
tion of guanine. M. A. W. 

GUANO V. Fbbtilisbes. 

6UAN0SINE, identical with Yernin 
Ci„H.305N„2H30, 
a compound of guanine and d-ribose, occurs in 
certain plants, and forms one of the products of 
hydrolysis of nucleic acid; it decomposes at 
237°, and has [o]^"— 60-52° (Levene and Jacobs, 
Ber. 1909, 42, 2469 ; Sohulze, Zeitsoh. physiol. 
Chem. 1910, 66, 128; Schulze and Trier, iftsd 
1910,70, 143). 

GUANYLUREA, Dicyandiamidine, v. Dl- 

CYANDIAMIDE. 

GUARANA {Uarana). Guarana is a dried 
paste prepared from the seeds of the Paullinia 
Cupana (H. B. and K.), a climbing shrub 
inhabiting the northern and western provinces 
of Brazil. It is made for the most part by 
different sections of the (Iruaranis, a tribe of 
South American Indians, and probably by dif- 
ferent methods. Generally, however, the ground 
or powdered seeds are moistened by exposure to 
dew, or by the addition of water, kneaded into a 
paste, made into cylindrical or globular masses 
and dried before fires, in chimneys, or by the 
heat of the sun. These cakes as they appear in 
commerce are hard, with a rough reddish-brown 
exterior, and somewhat lighter colour inside. 
They evolve a chocolate-like odour, and have a 
bitter astringent taste. In South America 



14 



GDARANA. 



guaiana is an ai-ticle of food used much in the 
same mannei as we employ . cocoa, and in 
European mediciuo it is admrnistered as a nervous 
stimulant for the relief of certain kinds of head- 
ache. JPor further details as to its source, 
preparation, and uses v. Cooke (Fharm. J. [iii.] 
1, 221) ; HaUaweU {Md. [iii.] 3, 773) ; Squibb 
{ibid, [iii.] 15, 165) ; Rusby (ibid, [iii.] 18, 1050) ; 
and Marsden (Annals Trop. Med., 4, 105). 

The physiological activity of guarana depends 
upon the presence of an alkaloid at first termed 
' gnaranine ' but afterwards found to be identical 
with caffeine (v. CAFFBruB) (Martius, Kastn. 
Archiv. 7, 266 ; Annalen,36, 93; Berthemotand 
Dechastelus, J. Pharm. Chim. 26, 518). Sten- 
house obtained the alkaloid by .extracting 
powdered guarana with about fifty times its 
weight of boiling water, and treating the solution 
when cold with basic lead acetate. A pre- 
cipitate of alkalo'd and salts of lead falls aom 
which repeated extraction with hot water 
removes the caffeine. The aqueous solution is 
freed from lead by sulphuretted hydrogen, 
evaporated to dryness, and the residue treated 
with hot alcohol. From this solution, on con- 
centration, crystals of the alkaloid are obtained, 
which may be purified by reorystallisation 
(Pharm. J. [i.] 16, 212). For other methods v. 
Greene {ibid, [iii.] 8, 87), who prefers to extract a 
mixture of guarana and three times its weight 
of litharge with boiling water ; 0. J. Williams 
(Chem. News, 26, 97), who exhausts a moistened 
and slowly liried mixture of guarana and lime 
jrith benzene ; Squibb, (Pharm. J. [iii.] 15, 165) 
and Bochefontaine and Gusset (Ch. Tech. C. 
Anzeiger, 4, 322), who treat a mixture of guarana 
and magnesia with weak alcohol and chloroform 
respectively. Kremel (Ph. Post. 21, 101) 
determines the cafieine in guarana by placing 
10 grams in a flask with 100 c.c. of 25 p.c. 
alcohol, noting the total weight, and digesting 
for 1 or 2 hours at 100°. The weight lost by 
evaporation is made up with similarly diluted 
alcohol, and 60 c.c. of the solution, corresponding 
to 5 grams of guarana, is separated by filtration, 
mixed with calcium hydroxide, and evaporated to 
dryness. The residue is extracted with chloro- 
form, from which the alkaloid is 'obtained in 
crystals, dried at 100° and weighed. The 
following percentages of caffeine are selected 
from published analyses of guarana ; 5-10, 5-04 
(Stenhouse); 5-05 (Greene); 4-20-5-00 (5 
samples, Feemster, Pharm. J. [iii.] 13, 363) ; 
4-5 (B. and Gusset); 3-12, 3-80 (Kremel). 
Feemster found in the seeds 5-08 p.c. and 
Peokolt (J. 1866, 709), in the shelled seeds 
4-81 p.c. ; seed shells 2-44 p.c. and pulp 4-29 p.c. 
Thorns (Pharm. C«nth. 1890, 533) however states 
that the proportion of caffeine in guarana has 
been overestimated, and this has been confirmed 
by Kirmsse (Arch. Pharm. 236, 122), who 
found in three samples 2-68, 2-97, and 3'10 p.c. 
respectively. 

Besides caffeine, guarauEt contains gum, 
starch, an acrid green fixed oil, a concrete volatile 
oil, and tannin (Fournier, J. Pharm. Chim. 1861, 
291). The tannin further examined by Greene 
(Pharm. J. [iii.] 8, 328) was found to behave to- 
wards reagents unlike previously known varieties, 
and the term pavUinitannic acid was, there- 
fore, applied to it. It forms a yellowish-white 
amorphous mass, having an astringent taste. 



It is easily soluble in water or alcohol. By 
extraction of the crude ttumin with ether, 
crystals are obtained identical with those of the 
oatechin of Pegu catechu (Kirmsse, I.e.). Kremel 
found l'3-2'0 p.c. <rf ash consisting chiefly of 
phosphates. 

A specimen of guarana examined by NiereU' 
stein, probably derived from PauUinia trigonia 
(Veil.), was found to contain an alkaloid, P-guara- 
nine. This was obtained in the form of small 
needles.m.p. 217°-219''; after drying, the sub- 
stance had the composition CjoHjjOjjiNt, The 
guarana contained 4-3 p.c. of tannic acid, which, 
after purification, was obtained in small colourless 
needles ; m.p. 199°-201''. The tannin, giuiraiia- 
tannic acid, appears to resemble the chlorogenio 
acid obtained from coffee (Gorter, Annalen, 358, 
327 ; 359, 217) rather than catechin, but is not 
identical with either of these substances (Annals 
Trop. Med. 4, 115). A. S. 

GUAVA. The fruit of Psidium Ouajava 
(Linn.). Prinsen-Geerligs (Chem. Zeit. 1897, 21, 
719), gives the following data : — 

The flesh contains 

Average Glu- Levu- Su- 

wt. in The fruit consists of cose lose crose 

grammes Flesh Skin Seeds p.c. p.c p.c. 

650 85-0 120 30 20 05 1-7 

H. I. 

GUEBNSET BLUE. A colouring matter be- 
longing to the Indtoinb group (?.».). 

GUIGNET'S 6KEEN v. CHBoiaTTU. 

GUINEA GREEN B. The sodium salt of 
the disnlphonic acid of diethyl- dibenzyl- di- 
amine- triphenyl- carbinol. Is a dark-green 
powder resembling Light-green S or Acid Green, 
V. Tbiphbnylmethaitb coloueing mattbes. 

GULAUCHA, GULOE, and GILOE. Indian 
names for Tinospora cordifolia (Miers.). This 
plant flourishes in India, the drag being sold 
extensively in the bazaars as a tonic and anti- 
periodic, in the form of cylindrical pieces 2-5 cm. 
long and 1-5 cm. in diameter. It is a perennial 
ereeper, climbing to the summits of the highest 
trees, its branches putting forth roots which, 
reaching to the ground, initiate a fresh growth. 
Boots, stems, and leaves are equally in demand 
as a drug. The Indian pharmacopoeia commends 
its use as a tincture (4-8 c.c. in die) ; as an 
extract (0-6-1 gram pet^diem) in the form of 
pills ; and as an infusion (1 : 10), of which 
60-90 c.c. , are to be taken thrice a day. The 
stems contain verberin, an uncrystaUisable 
bitter substance, changed by dilute sulphuric 
acid into a glucoside, and a bitter kind of starch 
meal known as ' palo ' (J. Soc. Chem. Ind. 6, 
49). 

GUM RESINS. This article includes the 
more important members of that group of pro- 
ducts which consist essentially of a mixture of 
gum and resin. They are generally the exudated 
mUky juice of plants dried by spontaneous 
evaporation. When triturated with water they 
give more or less perfect emulsions. Compare 
introduction to article Resins. 

Ammoniacam ; Oummi-resina ammoniacum. 
Oomme-risine ammoniaque, Fr. ; Ammoniak 
gummi-harz, Ger. 

Persian ammoniacum. The ammonia- 
cum of the early Greek physicians came from 
Africa, and was probably that variety known as 
African ammoniacum. The drug, which has 



GUM RESmS. 



15 



howevor since the tenth century been an article 
of European commerce, is obtained from Persia 
and neighbouring districts, reaching our markets 
according to Dymock (Fharm. J. [iii.] 6, 321) now 
generally by way of Bombay. It is the inspis- 
sated juice collected from the stems of the 
Dorema Ammoniacum (D. Don). For plates v. 
Bentl. a. Trim. 131. This plant attains a height 
of 6-8 feet, and the flow of juice from its stem 
is caused by punctures made by beetles. 

The gum-resin occurs in commerce as brittle 
grains oi tears oi roundish lumps, pale yellow 
externally and waxy milky-white within. It 
softens readily when warmed. In taste it is 
bitter and acrid, and it possesses a characteristic 
odour. Triturated with water it forms an emul- 
sion. A very complete account of the literature 
of ammoniacum, including the result of the 
examination of some twenty specimens, will be 
found in the memoir of Hirschsohn (Pharm. 
Zeit. 1875, 225; Pharm. J. [iii.] 7, 612, 710, and 
770). The sp.gr. of ammoniacum.is 1-207, and 
3 parts of it dissolve in 4 of alcohol. Hypo- 
chlorites, as fox example a solution of bleaching 
powder, impart to it a bright-orange colour, a 
character that serves to distinguish it from the 
African variety which is not afiected by these 
reagents. The allied gum-resin galbanum also 
gives no colour reaction with hypochlorites. 

Ammoniacum consists essentially of resin, 
gum, and a small proportion of volatile oil. The 
resin constitutes 70 p.o. of good specimens of 
the drug. A sample of ammoniacum examined 
by Luz (Arch. Pharm. 233, 640) contained 4-5 p.o. 
of water, 69 p.c. of resin, 22-7 p.c. of substances 
soluble in water, and 3-S p.o. of substances, 
other than resin, insoluble in water. A con- 
siderable amount of salicylic acid was present, 
but no aldehydes or terpenes. Normal butyric 
and valeric acids were also present largely in 
combination with a resin alcohol ammoreeinotan' 
nol CigHggOg, a chocolate-brown, tasteless and 
odourless powder, soluble in alkalis and acids. 
The resin consists essentially of ammoresino- 
tannol salicylate. It melts at from 35° to 60°, 
is soluble in alcohol, chloroform, glacial acetic 
acid, sulphuric acid, and alkalis, partly soluble 
in carbon disulphide, benzene, and solution of 
ammonia, and insoluble in light petroleum. 
Sommer (J. 1869, 573) was unable to obtain 
umbelliferone from the gum-resin, but resor- 
cinol, C,H,(0H)2, and protooatechuio acid, 
C,H3(OH)2COOH, are formed when it is fused 
with potash (Hlasiwetz and Barth, Annalen, 
130, 354). It yields styphnic acid, trinitro- 
resorcinol, C„H(NOa)a{OH)a, when treated with 
nitric acid (WUl and Bottger, Annalen, 68, 269 ; 
cf. Schwanert, ibid. 128, 123). 

Ammoniacum gum is partly soluble and 
partly insoluble in water. The insoluble portion, 
which constitutes a fourth of the gummy con- 
stituents, appears to be identical with the similar 
bassorin-like gums which occur in asafoetida and 
galbanum. When treated with 20 p.c. hydro- 
chloric acid, besides humus substances, it yields 
laevulic acid, and, on oxidising with nitric 
acid, 31 ■$ p.c. of mucic acid (equivalent to 
41-76 p.c. 01 galactose), but no saccharic acid. 
When distilled with dilute hydrochloric acid, it 
yields 9-36 p.c. furfuraldehyde (equivalent to 
16-67 p.c. of^ arabinose), and when boiled with 
dilute sulphuric acid reducing sugars are ob- 



tained, consisting chiefly of galactose (Erisch- 
muth, Chem. Zentr. 1897, ii. 1078). 

Volatile oil of ammoniacum exists only to 
the extent of \ p.c. Hirschsohn obtained no 
volatile oil by distillation with water, but light 
petroleum gave him 1-4-6-7 p.c. of volatile oily 
residues. Eluckiger and Hanbury describe the 
oil as unhke that of galbanum, posses»ng in a 
high degree the odour of the drug, and being 
free from sulphur. 

To test ammoniacum for galbanum resin 
5 grams is boiled with 15 grams of strong hydro- 
chloric acid for 15 minutes, 16 c.c. of water is 
then added, and the liquid filtered through a 
wetted, double filter ; ammonia is added to the 
clear filtrate when a blue fluorescence reveals the 
presence of galbanum (Dieterich. Chem. Zentr. 
1896, ii. 1137). For method of examination and 
table giving analytical constants, see Dieterich, 
I.C., and Pharm. Centh. 40, 467. 

Ammoniacum is employed in medicine in- 
ternally as an expectorant, and externally as a 
constituent of plasters. 

African ammoniacum. This, according 
to Hanbury (Pharm. J. [iii.] 3, 741), is the ammo- 
niacum of Dioscorides and the older writers. It 
is derived, according to Lindley (Pereira, Mat. 
Med. 1853, 1715), from the Ferula tingitana 
(Linn.), a plant inhabiting the African coast of 
the Mediterranean Sea. 

African ammoniacum, which is scarcely 
known in European markets, is described by 
Pereira as consisting of dark-coloured masses 
which internally have much the appearance 
of the Persian variety. The odour is, however, 
quite distinct. It forms an emulsion with water. 
Moss examined a specimen in 1873 (Pharm. J. 
[iii.] 3, 742) which consisted of resin 67-76 p.c, 
gum 9-01 p.c., water and volatile oi7 4-29 p.c, 
and bassorin and insoluble matter 18-86 p.c. It 
contained 13-47 p.c. of ash. It softened 
between the fingers more readily than Persian 
ammoniacum. Similar results were obtained by 
Hirschsohn By distilling it, however, the last 
observer isolated umbelliferone 

C,H3(OH)<g^^55=£-0: 

Goldsohmiedt (Ber. 11, 850) announces that by 
fusion with potash African ammoniacum 3^elds 
resorcinol, together with an acid CuHjoOg. 
This acid is not produced when the Persian 
drug is similarly treated. 

Asafoetida ; Oummi-resina Asafoetida. Asa- 
foetida, Ft. ; Asant, Stinkasant, Teufelsdreck, Ger. 

Gum-resin asafoetida is the dried juice of the 
roots of two large herbaceous plants which in- 
habit Tibet, Afghanistan, Turkestan, and the 
country from the Sea of Aral to the Persian 
Gulf. These are the Ferula NarChex (Boissier) 
and the Ferula foetida (Kegel). For drawings 
V. Bentl. a. Trim. 126-127, and Holmes (Pharm. 
J. [3] 19, 21, 41, and 365). Details of the 
mode of. preparing the roots and of collecting 
the dried exudation are given by Fliickiger and 
Hanbury (Fliiok. and Hanb. 316) and by Pereira 
(Mat. Med. 1853, 2, 1704). It is certain that 
asafoetida was known to the- Arabian writers of 
the tenth century, and there is reason to 
believe that a knowledge of the drug is far 
more ancient. 

Supplies of asafoetida are now almost entirely 
derived by way of India from Afghanistan. It 



16 



GUM RESINS. 



occurs as teais more or less agglutinated, and 
sometimes as a honey-like mass. It is often 
largely mixed with earthy matter. A character- 
istic property of the drug is that when broken 
the milky white surface changes gradually to a 
pink, which passes into a brown hue. Touched 
with nitric acid (sp.gr. 1-2) it gives a green 
colour. With water it forms an emulsion. The 
tears are brittle, and may be powdered when cold. 
Asafoetida has a powerful alliaceous odour and 
an acrid bitter alliaceous taste. 

The chief constituents of asafoetida are resin, 
gum, and volatile oil. For results of early in- 
vestigations V. Gm. 17, 398. The analysis of Pel- 
letier (Bull. Pharm. 3, 556) shows that the resin 
amounts to 65-0 p.c, the soluble gum 19-44 p.c, 
the insoluble gum 11-66 p.c, and the volatile oil 
3-6 p.c, or, according to FlUckiger and Hanbury, 
6-9 p.c. The resin is only partjy soluble in 
ether and chloroform, but is entirely dissolved 
without alteration by concentrated nitric acid 
(c/. Johnston, PhU. Trans. 1840, 354). Hlasi- 
wetz and Barth (Annalen, 138, 64) discovered in 
the resin ferulic acid, the methyl phenolic ether 
of hydroxyoinnamic or caffeio acid, 

C8H,(CH:C!H-COOH)(OCH3)(OH)l : 3 : 4 
An alcoholic solution of asafoetida is precipitated 
by an alcoholic solution of lead acetate, and from 
the insoluble lead salt the ferulic acid is re- 
generated. It consists of needles melting at 
168°-169° (Tiemann, Ber. 9, 416). Vanillin was 
shown to be present in asafoetida by Schmidt 
(Arch. Pharm. [3] 24, 634). 

Pure drops of Asafcetida amygdaloides 
examined by Poldsek (Arch. Pharm. 235, 125), 
gave the following results : resin, soluble in 
ether, asaresinotannol ferulate, ^ 61 -40 ; resin, 
insoluble in ether, free asaresinotannol, 0-60 ; 
gum, 25-1 ; essential oil, 6-7 ; vaniUln, 0-06 ; 
ferulic acid, 1-28 ; moisture, 2-36 p.o. On 
hydrolysis with potassium carbonate, the 
soluble resin yields asaresinotannol and ferulic 
acid ; with sulphuric acid, however, it is 
hydrolysed into the same tannol and umbelU- 
ferone. Asaresinotannol is a brownish-yellow 
amorphous substance, and has the composition 

When asafoetida resin is distilled alone, 
variously tinted oils are obtained, with J 
p.c. of umbelliferone (Sommer J. 1859, 673). 
Fused with potash, resoroinol and protocatechuio 
acid are formed (Hlasiwetz and Barth), and 
treated with nitric acid it yields trinitroresor- 
cinol or etyphnio acid (Will and Boettger, 
Annalen, 68, 269). 

The gum of asafoetida consists of two portions, 
the one soluble and the other insoluble in water. 
The volatile oil is described by Muckiger and 
Hanbury as of a light-yellow colour with the 
odour of asafoetida. The taste is at first mUd 
and then irritating, but it does not stimulate 
when applied to the skin like mustard oil. 
The oil is neutral, but becomes acid by ex- 
posure to the air, at the same time evolving 
sulphuretted hydrogen. By fractional distilla- 
tion of the oil undo^ reduced pressure, Semmler 
(Ber. 23, 3530; 24, 78) finds that it contains 
two terpenes CioHu ; a substance (C,oH,jO)», 
which gives a sesquiterpene CigHji when acted 
upon by sodium ; an oil C.HijSj boiling at 
210°-212° with slight decomposition ; and an 
oil CiiHj.^j, which decomposes on distillation 



under the ordinary pressure with evolution of 
most repl:^lsive smelling gases. 

Asafoatida is used in medicine as a nervous 
stimulant and antispasmodic, and in the East as 
a condiment. 

Other varieties of asafcstida. The 
Hing used by the natives of Bombay is a 
variety of asafoetida. It is derived from Ferula 
alliacea (Boissier). It is more repulsive, and 
contains a larger proportion of volatile oil than 
asafoetida (Fluckiger, Pharm. J. [iii.] 6, 401 ; 
Pluck, a. Hanb. 319). 

Bdellium. 

Indian Bdellium- False Myrrh; Bdel- 
lium. This is the bdellium of the Bible, and is 
now used chiefly as an adulterant of myrrh. It 
is the product of Balsamodendron Miikul (Hooker) 
and, according to Dymock, also of the B. Box- 
burgii (Arnott) (cf. Pharm. J. [iii.] 6, 661). Both 
are indigenous to India, but grow perhaps also in 
Southern Arabia. The gum-resin breaks with 
a flat conchoidal fracture, and though somewhat 
darker in colour, it resembles myrrh in appear- 
ance. It may be distinguished from myrrh by 
its not giving the violet colour reaction (w. 
Myrrh). (For analytical constants of bdeUium 
V. Dieterich Pharm. Centr. 40, 467.) 

African Bdellium. A more highly es- 
teemed bdellium, the product of BaUamodendron 
africanum (Arnott), a shrub indigenous to West 
Africa. It is used in France as a constituent of 
plasters. In fracture and other respects it re- 
sembles myrrh, hut it does not give the violet 
colour reaction {v. Myrrh). African bdellium 
was analysed by Pelletier (Ann. Chim. Phys. [ii.] 
80, 38), who found resin 59 p.c, soluble gum 
9-2 p.c, insoluble gum 30-6 p.c, volatile^ oil and 
loss 1-2 p.c. The resin was further examined by 
Johnston (Phil. Trans. 1840, 368). Cf. Bley 
and Diesel (Arch. Pharm. [ii.] 43, 304). 

Euphorbium. Oomme-rtiine d'Euphorbe, Fr. ; 
Euphorbium, Ger. This extremely acrid drug 
has been known since the time of Diosoorides, 
but it is now very seldom employed in medicine. 
It is the inspissated milky juice of the Euphorbia 
resinifera (Berg), a cactus-like plant inhabiting 
Morocco and neighbouring districts of Northern 
Africa. A drawing is given by Bentl. a. Trim. 240. 
Euphorbium consists of irregular masses of a 
waxy-yellow or brown appearance, often inclos- 
ing spines and other fragments of the plant. It 
has a slight aromatic odour and an extremely 
acrid taste, its dust causing violent and even 
dangerous irritation to the nose or throat. 

FlUckiger (Fliick. and Hanb. 660) found a 
selected specimen to consist of amorphous resin, 
38 p.c. ; euphorbon, 22 p.c. ; mucilage, 18 p.o. ; 
malate of calcium, sodium, &c, 12 p.c. ; mineral 
compounds, 10 p.c. It contains no volatile oil. 

Examined by Tsohirch and Paul (Arch. 
Pharm. 234, 249) 100 parts of the drug were 
found to contain euphorbic acid, 0-7 ; euphor- 
bone, 40 ; amorphous resins, 21 ; malates, 25 ; 
carbohydrate, 2 ; impurities and loss, 11. 
Euphorbic acid, which is extracted from an 
ethereal solution of the resin by 1 p.c. aqueous 
ammonium carbonate, is amorphous! has the 
m.p. 107°-108° and the composition Cj4H8„Oe. 
Euphorhone CaoH^gO is best obtained from the 
drug by extraction with light petroleum and 
crystallisation first from alcohol and then re- 
peatedly from acetone. It melts at 116°-116°. 



GUM RESINS. 



17 



EiipJiorioreaene C^a'B.tfii remains as an amor- 
phous mass, m.p. 74°-76°, alter steam distillation 
for some weeks of the resin freed from euphor- 
bone and mixed with aqueous potassium hy- 
droxide. Xhe residual alkaline liquid, on being 
acidified, gives an amorphous precipitate of 
a-euphorboresene C^sHjgO, which melts at about 
76°, and is now insoluble in dilute aqueous potas- 
sium hydroxide. From an aqueous extract of 
the drug calcium malate was isolated ; also a 
dextrorotatory carbohydrate precipitated by 
alcohol, and another, possibly a pentosan, 
which remained dissolved. 

When a filtered light petroleum extract of 
euphorbium resin is floated on a solution of 
one drop of concentrated sulphuric acid in 
20 CO. 01 water, a very stable blood-red layer is 
formed at the surface where the two liquids 
touch ; on shaking, the whole of the acid liquid 
becomes red, and this colour only slowly changes 
to brown. This reaction may be used for 
purposes of identification ; an extract of the 
most suitable concentration is obtained from 
0-1 gram of euphorbium and 10'o.c. of light 
petroleum. 

Euphorbium is now used only in veterinary 
medicine. Applied externally to the human 
subject it is irritant and vesicating, and internally 
administered it causes violent vomiting and 
purging. It is said to be an efficient preservative 
of iron and steel against corrosion (Year Book 
Pharm. 1880, 344). 

Galbanum; Gummi-resina Galbanum. Oal- 
banum, Fr. ; Mutterharz, Gee. Galbanum has 
entered into the constitution of incense, and 
has been employed in medicine from the earliest 
times. It was used by the Israelites, and was 
well known to Hippocrates, Theophrastus, and 
Dioscorides, also to the Arabians, and still retains 
its place in the official pharmacopoeias of Europe 
and the United States. But notwithstanding 
its antiquity, the- precise plant from which 
galbanum is derived still remains uncertain. It 
is most probably obtained from the Ferula gal- 
baniflua (Boissier and Buhse), and perhaps from 
other allied species of Ferula, natives of Persia. 
For figure v. Bentl. a. Trim. 128 (c/. Holmes, 
Pharm. J. [in.] 19, 365). 

The gum-resin occurs in commerce in 
drops or tears, usually adhering into solid 
masses. In colour it exhibits various shades of 
light yellowish-brown, sometimes tinted with 
green. The odour of galbanum is aromatic, and 
the taste unpleasant, bitter, -and alliaceous. 
Fliickiger and Hanbury (Fliick. a. Hanb. 323 ) note 
that when galbanum is warmed with concentrated 
hydrochloric acid a red colour is developed, 
which on the careful addition of spirit of wine, 
turns violet or bluish. Asafoetida treated in the 
same manner assumes a dingy colour, whilst 
anmioniacum gives no colour change at all. 
Further details of the characters of galbanum 
and its behaviour towards reagents are given in 
an elaborate memoir by Hirschsohn (Pharm. 
Zeit. 1876, 225; Pharm. J. [iii.] 7, 369, 389, 
429, 631, and 571). This observer divides 
galbanum of commerce, according to its physical 
character, into three varieties, one coming from 
Persia and two from the Levant, or, according 
to its behaviour towards reagents, into four 
sorts — one from Persia and three from the 
Levant. 

Vol. ni.-r. 



Galbanum reain examined by Conrady 
(Arch. Pharm. 232, 98) was found to contain 
9-6 p.c. of ethereal oil; 63 '5 p.c. of a resin 
soluble in alcohol ; and 27-0 p.c. of impurities 
and gum. , The pure resin obtained from the 
commercial product by extraction with alcohol 
and subsequent treatment with sodium salicy- 
late contains 20 p.c. of combined umbelliferone ; 
60 p.c. of galbaresinotannol ; and 0-25 p.c. of 
free umbelliferone. The resin which most 
probably consists of a galbaresinotannylic salt 
of umbelliferone is best hydrolysed by sulphuric 
acid since umbeUiferone is unattacked by this 
reagent. Galbaresinotannol on analysis gives 
numbers agreeing with the formula CuHaoOa ; 
on distillation with phosphoric anhydride it 
yields a hydrocarbon CijHj,, and, on oxidation 
with nitric acid, camphoric and camphoronio 
acids. The volatile oil is obtained by distilla- 
tion with water' or by extraction with light petro- 
leum. According to Fliickiger and Hanbury, 
the crude oil possesses an aromatic taste and is 
dextrorotatory. On the addition of bromine to 
the oil extracted from Persian galbanum a red 
to violet or blue colour appears. The oil con- 
sists partly of a hydrocarbon CiqH,, which gives 
a crystalline hydrochloride C]oH,j,HCl. The 
chief part, however, is a mixture of heavier 
hydrocarbons [cf. Moessmer, Anualen, 119, 
237). 

When galbanum resin is distilled a small 
quantity of umbelliferone is obtained (Sommer, 
J. 1859, 673). This compound is now known to 
be a product of the distillation of many other 
resins or gum-resins, especially those of the 
■Umbellifera. Galbanum yields 0-83 p.c, saga- 
penum 0'32 p.c, asafoetida 0-28 p.c. Syntheti- 
cally, umbelliferone may be produced, as pointed 
out by Peohmann (Ber. 17, 932), by acting upon 
a mixture of resorcinol and maUc acid with 
dehydrating agents such as sulphuric acid, thus : 
CeH4(OH)a+C3H3(OH)(COOH), 

=CeH3(OH)<^Q^^zS:^+HCOOH+2HjO 

Another product of the destructive distillation of 
galbanum resin is a thick brilliant blue oil. 
The oil deposits in the cold crystals of umbellife- 
rone. It has a bitter acrid taste and aromatic 
odour. Kachler (Ber. 4, 36) separated it into 
a colourless hydrocarbon C,(,H,5 boiling at 240°, 
and a blue oil C,oHi,0 which boiled at 289°. 
The flowers of the wild chamomile Matricaria 
Chamomilla (Liim.)yielda blue oil very similar 
to that obtained from galbanum. Both oils are 
converted by potassium into the hydrocarbon 
CioH,j, which on the addition of bromine 
vapour gives the blue colour reaction. Hlasi- 
wetz and Earth (Annalen, 130, 354) have shown 
that by fusing galbanum resin with potash as 
much as 6 p.c. of resorcinol is formed {cf. Gold- 
schmied, Ber. 11, 850); and by treatment with 
nitric acid. Will and Boettger (Annalen, 68, 
269) obtained styphnio acid {cf. Schwanert, 
Annalen, 128, 123). 

Hirschsohn in his experiments, after removal 
of the volatile oil and resin and a little sac- 
charine and astringent matter, by extraction of 
galbanum with light petroleum, ether, and 
85 p.c. alcohol, successively, treats the residue 
with water to obtain the gum. The yield was 
6-17 p.c. The sugar obtained from this gum 



18 



GUM RESINS. 



by the action of dilute acids is optically distinct 
from that produced in the same way from gum 
arabic. 

Galbanum is administered in medicine in- 
ternally as an expectorant, and externally it 
is appUed in the form of plasters. 

A table of the acidity, ether, and saponifica- 
tion numben of galbanum resin is given by 
Keterich (Pharm. Centh. 40, 467). 

Gamboge. Cambogia, Cadie Gum, Qwnimi 
Oanibogia, Oummi Cfutti. Oomme Gvite, Fr. ; 
GhUti, OwmmigvM, Ger. This beautiful orange- 
red gum-resin comes to us from Camboja, 
Siam, and Cochin China, where it is the product 
of a laurel-like tree, the Garcinia Hanburyi 
(Hook.) ; V. Bentl. a. Trim. 33. Gamboge was 
known to the Chinese in the thirteenth century, 
but it was not until the serenteenth century 
that it appeared in European markets. For the 
purpose of collecting it the trees are incised, and 
sections of bamboo are attached to collect the 
milky juice, which, hardening by evaporation, 
takes the cylindrical shape of the receiving 
vessel. Gamboge as it occurs in commerce is 
brittle, and may be powdered readily. In 
presence of water it forms at once a yellow 
emulsion. It has a disagreeable and acrid taste. 

Among the earliei investigators who analysed 
gamboge are Braoonnot ( Ann. Chim. Phys. [i.] 68, 
33), John (Chem. Schriften, 4, 193), Unverdorben 
(N. Jour. Trommsdorf. 8, 1, and 60), Christison 
(Annalen, 23, 185); Johnston (Phil. Trans. 1839, 
281),' and Bilchnei (Annalen, 4S, 72). Costelo 
(Amer. J. Pharm. 1879, 174), finds the resin to 
vary from 68 to 79 p.c, and the gum from 19 to 27 
p.c. (c/. Hurst, Pharm. J. [iii.] 19, 761). Thegum 
is extracted by water. Its solution, like arable, is 
not precipitated by neutral lead acetate, but its 
behaviour towards other reagents shows it to 
be a difieront gum. By the action of dilute 
acids it yields a non-JermenigMe sugar, and 
when oxidised by nitric acid, mucio acid 
04H4(OH)i(COOH)a is formed. 

Alcohol dissolves the resin. It combines 
with bases, and is called by Johnston gamhodic 
acid. By fusion with potash, Hlasiwetz and 
Barth (Annalen, 138, 68) obtained a number of 
interesting products. Besides several acids of 
the fatty series, these observers isolated phloro- 
glucinol CoH,(OH)a(l : 3 : 6) ; pyrotartario acid 
CH,-CH(COOH)CHj-COOH ; and isomesidic, iso- 
uvitic, or isovitinic acid C,H4-CH2(C00H)C00H. 
This last-mentioned acid has since been pro- 
duced by the action of hot dilute alkali on benzyl- 
oyanide-o-carboxylio acid CN-CH2-C,H4-C00H, 
which converts the cyanogen into a oarboxylio 
group (Wislicenus, Aimalen, 233, 106). 

For the detection of gamboge in mixtures, 
V. Hirschsohn (Pharm. Zeit. '24, 609). In medi- 
cine gamboge is employed as a drastic purgative, 
usually in combination with other substances. 
It is also an important colouring agent. 

Ivy gum resin. Owmmi-resina Hederx. In 
Southern Europe and in the Levant a gum-resin 
is obtained from the old trunks of the common 
ivy, Eedera Helix (Linn.). It consists of irregular 
masses of a reddish or yellowish-brown colour 
externally, but showing a deep red by transmitted 
light. The taste is bitter and acrid, but when 
heated it evolves a balsamic odour. Pelletier 
(Bull. Phai-m. 4, 504) found the gum-resin to 
consist of resin 23 p.c, gum 7 p.c, and 70 p.c. 



of woody fibre. Examined by Sommer (Arch. 
Pharm. [ii.] 98, 11) it gave no umbelliferone. 

Besides the gum -resin the leaves, berries, and 
the wood itself of ivy have been used in medicine 
and they have been examined by chemists. 
Hartsen (J. 1876, 827) found ivy leaves to con- 
tain a glucoside allied to saponin, and this was 
afterwards studied by Davies and Hutchinson 
(Pharm. J [iii.] 7, 275), Davies {ibid, [iii] 8, 205), 
Kingzett {ibid, [iii.] 8, 206), Vernet (J. 1881, 91), 
Vincent (Bull. Soc chim. 35, 231), and Block 
(Arch. Pharm. [iii.] 26, 953). Most of these 
observers obtained the glucoside from ivy 
berries. Davies and Hutchinson regard it as 
identical with the hederio acid which, togethei 
with hederotannie- acid, Posselt found in ivy 
berries (Annalen, 69, 62). 

Hederic acid or ivy glucoside CsjHs^O,, is 
deposited in needles from the alcoholic 
extract of ivy berries that have been pre- 
viously exhausted with ether (D. and H.), 
or the berries may be exhausted with alcohol, 
and the residue, after the alcohol has been 
removed by distillation, washed in the cold 
with benzene and extracted with hot acetone. 
On concentrating the solution a crystalline mass 
is obtained which is purified by recrystaJlisation 
from alcohol (Vernet ; Vincent)i The glucoside 
forms silky needles which melt at 233°. It is 
insoluble in water, chloroform, o> light petro- 
leum, is slightly soluble in cold acetone, 
benzene, or ether, and very soluble in hot 
alcohol and alkalis. It is inodorous, but pos- 
sesses the taste of the berries. By the action 
of dilute acids it breaks up into a crystalline 
compound CjoHijOe (?), which melts at 278°-280° 
and a non-fermentable sugar which reduces 
Pehling's solution. 

Houdas (Compt. rend. 128, 1463) has separ- 
ated from ivy a glucoside h&ierin Gffii^fii,, 
which crystallises from alcohol in thin needles, 
melting at 248°. When hydrolysed with dilute 
sulphuric acid hederin gives rise to an insoluble 
product hederidin, and to two sugars hederose 
and rhamnose. Hederidin CjeHtgOi crystallises 
from boiling alcohol in sparkling prisms, which 
melt at 324°, and sublime undecomposed. 
Hederose CeHi^O, crystallises in shining needles, 
and is very soluble in water or boiling alcohol. 
It melts at 155°, and is dextrorotatory. 

The physiological action of ivy and hederin 
has been studied by Joanin (Compt. rend. 128, 
1476). 

Myrrh. Myrrlia ; Heerabol Myrrh ; Gummi- 
resina Myrrha. Myrrhe, Fr. ; Myrrhe, Ger. To- 
gether with oUbanum, myrrh has been used as a 
constituent of incense from the earliest times. 
It is mentioned in Genesis and in other places 
in the Bible. The Egyptians employed it not 
only in fumigations, but also in embalming and 
in medicine. It has retained its place down 
to the present day, and is included in all the 
pharmacopoeias. Myrrh is the spontaneous gum- 
resinous exudate of the shrubs or small trees of 
the Salsamodendron Myrrha (Nees), an inhabi- 
tant of the Somali coast of the Gulf of Aden and 
of the Red Sea coast of Arabia (Trimen, Pharm. J. 
[iii.] 9, 893). A drawing of the tree is given by 
Bentl. a. Trim. 60. The exudate is aUowed to 
harden on the tree before collection. It occurs 
in irregular-shaped masses of a red-brown 
colour and dusty appearance. When cold it is 



GUM RESINS. 



19 



brittle, and breaks with an uneTen, waxy, oily- 
looking fracture, often ezhibitinglighter-coloured 
semicircnlai striations. With water it readily 
yields an emulsion. The odoui of myrrh is 
fragrant and agreeable, and the taste bitter, 
aromatic, and acrid. 

The chief constituents of myrrh are gum, 
resin, and volatile oil. The relative proportions, 
even in the case of true myrrh, vary greatly in 
different specimens. Generally the gum con- 
stitutes 40-65 P.O., the resin 25-40 p.c., and the 
volatile oil is said to reach 4-4 p.c. Fliickiger 
and Hanbury (Fliick. a. Hanb. 143) found 27 
p.c. of resin in a good specimen, and Kohler 
(Arch. Pharm. 228, 291) found 7-8 p.c. of vola- 
tile oil. Briickner's analysis (Neues Bep. Pharm. 
16, 76) gave : soluble in water, gum, 67'76 
p.c. ; resin soluble in carbon disulphide, 14-06 
p.c. ; resin soluble in ether, 12-57 p.c. ; resin 
insoluble in ether, 4-81 p.c. ; substances soluble 
in diluted alcohol, 0-43 p.c. ; insoluble (sand, 
bark, &o.), 0-38 p.o. 

Myrrh resin is soluble in alcohol or chloro- 
form, but it is only partly soluble in ether, 
carbon disulphide, or alkalis. According to 
Kohler (I.e.) it is a mixture of several resins, the 
greater portion of which is a soft resin C2eH3t05 
soluble in ether. There are also present 
two dibasic acids CuHuOig and CjeHjaOs 
respectively. 

Tschirch and Bergmann (Arch. Pharm. 243, 
641) have made an examination of Myrrha electa, 
which is the true or Heerabol myrrh obtained 
by sorting from the other resins mixed with 
which myrrh is imported into the United 
Kingdom. By extraction of the ethereal solution 
with 1 p.o. aqueous potassium hydroxide two 
amorphous greyish-yeUow neutral substances 
were obtained ; a-heerabo-myrrlwl C^-iK^fi^, 
m.p. 158°-165'', which is precipitated from 
alcoholic solution by lead acetate, and ff-heerabo- 
myrrhol CisHjjOi, m.p. 116°-124°, not precipi- 
tated in tins way. IVom the residue insoluble 
in ether, alcohol extracted two brown amorphous 
substances, a-heeraho-myrrholol CjsHjjOj or 
OsoH440i^,m.p. 207°-220°, and $-heerabo-myrrho- 
lol CasHjaOio, m.p. 205°-213''. These differ in 
their behaviour towards lead acetate. The 
portion of the resin soluble in ether but insoluble 
in alkali consists of heeraboresene CjgHioO^, 
m.p. 98°-104°. IVom the portion of the resin 
of Myrrha electa, insoluble in light petroleum, 
but soluble in ether, von IViedrichs (Arch. 
Pharm. 245, 427) isolated the following com- 
pounds ; a-commiphoric acid CuHjjOi, m.p. 
201°-203° ; 0-commiphoric acid Ci4Hij04, m.p. 
205° ; y-commiphoric acid CuH^jOj, m.p. 169°- 
172°; a-herrabo-myrrhol CigHjsOj, m.p. 248°- 
260°; p-heerabo-myrrhol CjoHjjOe, m.p. 168°.; 
commiphorinic acid CjjHajOg, m.p. 135° ; a 
yeUow alcohol CuHajOj, b.p. 264° ; and herra- 
__ boresene Oifi^fi,, m.p. 100°-102° ; and from the 
portion of the resin insoluble both in light 
petroleum or ether, a-heerabo-myrrhololic acid 
CijHjaOf, m.p. 220°-225°, and fi-keerabo-myrr- 
hololic acid C25H32O,, m.p. 187°-190°. 

Myrrh resin gives a violet colour when a frag- 
ment moistened with alcohol is treated with nitric 
acid, but the colour is not so marked as in the 
case of galbanum (c/. Ruickholdt, Arch. Pharm. 
Hi.] 41, 1 ; Held, Annalen, 63, 59 ; Hager, Pharm. 
Centh. 1868, 68). Distilled, it gives no umbelli- 



ferone, but by fusion with potash Hlasiwetz and 
Bajth (Aimalen, 139, 78) obtained small quan- 
tities of catechol and protocatechuio acid. The 
property of giving a violet colooi when oxidised 
by nitric acid, or better, by bromine vapour, is 
confined to that resin which dissolves in carbon 
disulphide, and which, according to Bruckner, 
contains 75-6 p.c. of carbon. 

The gum of myrrh on analysis gives numbers 
agreeing with the formula C,HioOb. On treat- 
ment with hydrochloric acid it yields levulic 
acid (Kohler). It contains an enzyme which 
has the properties of an oxydase (Tschirch 
and Bergman ; von Priedriehs). 

The quantity of volatile oil in m3rrrh varies 
very greatly. The oil, according to Euickholdt, 
has the composition CioH,,©. Gladstone (Chem. 
Soc. Trans. 17,,11) describes it as a viscid brown- 
ish-green oil that, boiling at 266°, gave an 
oxidjsed product. Its sp.gr. was 1-0189. The 
oil prepared by Fluokigei (c/. Ber. 9, 471) was 
lighter than water, the sp.gr. at 13° being 0-988, 
and the boiling-point 270°-290°. Redistilled 
in a current of carbon dioxide it passed over 
between 262° and 263°. After redistillation the 
oil, on addition of a drop of nitric acid, gave 
after an hour or two a permanent violet hue, 
but this is better observed when bromine vapour 
is applied to a solution of the crude oil in carbon 
disulphide. 

. Samples of the oil examined by Lewinsohn 
(Arch. Pharm. 244, 412) contained cuminalde- 
hyde up to 1 p.c. and small quantities of eugenol 
and m-cresol, and of acetic and palmitic acids. 
By distillation over sodium, pinene, dipentene, 
and limonene were isolated, and in one com- 
mercial sample, a fourth terpens CioHj,, b.p. 
78°-80° (20 mm.). Two other possibly new 
sesquiterpenes CibHjj, b.p. 151°-154° (15 mm.) 
and b.p. 163°-168? (12 mm.) respectively, were 
obtained from two other samples of the oil. 
Von Friedrichs (I.e.) obtained from the essential 
oil, formic and acetio acids ; a crystalline acid, 
m.p. 159° ; m-cresol ; cuminaldehyde and 
cinnamaldehyde ; crystalline monobasic myrr- 
holic acid CijHjaOj, m.p. 236° ; and, the sesqui- 
terpene heerabolene CijHjj, b.p. 130°-136° 
(16 mm.). 

According to Huokiger, the bitter constituent of 
myrrh is a gluooside. v. Bolton (Zeitsch. Elektro- 
chem. 14,211), by extracting myrrh with alcohol, 
evaporating to drjmess and then extracting ' 
with water, obtained a substance burseracin, 
which forms 1-5-2 p.c. of the original drug. It 
is a yellow hygroscopic powder, m.p. 78°, and 
has the composition CjoHjgOj. It is not a 
glucoside. On treatment with hydrogen peroxide 
a compound is obtained, which appears to be 
radipactive. 

' Myrrh is a reputed stimulant and tonic, but 
its employment in medicine depends chiefly on 
its aromatic properties. 

Other varieties of myrrh. Several gum- 
rSsins more or less resembling true myrrh are 
occasionally found in commerce. Two are de- 
scribed by Fliickiger and Hanbury. One of these, 
often incorrectly called East Indian myrrh, but 
which is really an African drug, is known as , 
bisabcl or hebbakhade. In outward appear- 
ance it is very similar to true myrrh, but it is 
more acrid, and its resin, soluble in carbon disul- 
phide, gives no violet colour with bromine 



20 



GUM RESINS. 



vapour. An analysis of bisabol-myrrh from 
Somaliland gave the following results : gum 
soluble in water, 22-1 ; gum soluble in soda, 
29-85; resin, 21-5; bitter principles, 1-3; 
volatile oil, 7-8 ; water, 3-17 ; and inorganic 
matter, &c., 13-4 p.c. (Tucholka, Arch! Pharm. 
235, 289). 

The other variety is Arabian myrrh. It is 
collected in Southern Arabia east of Aden, and 
is probably the product of a distinct species 
(Hanbury). It is very nearly related to true 
myirh in appearance, and some specimens give 
the violet colour reaction. 

OUbanum, Frankincense ; Oummi-resina Oli- 
hanv/m ; Thus mfiseulum. Encens, Fr. ; Weiratich, 
Ger. Olibanum or frankincense has been the 
favouijte basis of incense from the earliest 
times. It is frequently referred to in the Bible, 
and the Egyptians employed it for fumigations 
and for embalming. 

Buemichen, in his book on the Paintings of 
the Temple of Dayr el B&hii in Upper Egypt, 
which represent the traific between Egypt and 
a land called Punt as early as the seventeenth 
century B.C., has shown that these paintings 
include, not only representations of olibanum in 
bags, but boxes or tubs containing living oliba- 
num trees. Tribute offerings of frankincense 
were common throughout the ancient world. 
At the present day the incense of the Boman 
and Greek Chruches is largely composed of 
olibanum. 

The gum-resin is the dried exudated juice of 
several species of BoswelUa. These trees, the 
fragrance of which is noticeable even at a dis- 
tance, inhabit Eastern Africa, near Cape Gar- 
dafui, and the southern coast of Arabia. They 
were studied by Birdwood (Trans. Linn. Soc. 27, 
111, 148). One of them is figured by Bentl. and 
Trim. 58 (Fluck. a. Hanb. 134). Olibanum is 
a solid which softens in the mouth, and has a 
slightly terebinthinous, not disagreeable, taste. 
It consists of tears of various shapes, generally 
detached. The odour, especially on heating, is 
pleasantly aromatic. It has a pale yellow oi 
' brown colour, and the larger fragments are more 
or less milky and translucent. Triturated with 
cold water it yields an emulsion. 

The chief constituents of frankincense are 
reain, gum, and volatile oil. The oil is obtained 
by distillation ; alcohol dissolves the resin and 
water the gum. Braconnot (Ann. Chim. Phys. [i.] 
68, 60) found resin 56 p.c, soluble gum 30 p.c, 
insoluble gum 6 p.c, and volatile oil 8 p.c. ; 
whilst the analysis of Kurbatow gave resin 72 p. c, 
gum 21 p.c, and volatile oil 7 p.c. (Zeitsch. 
Chem. [ii.] 7, 201). Prom the resin Tschirch 
and H^bey (Arch. Pharm. 236, 487) obtained 
boswellic acid CjjHsjOj, a white powder, 
m.p. 150°, which shows little tendency to 
crystallise. The resin probably contains bos- 
wellic acid in the form of an ethereal salt, and also 
oUbano-resene (CnHjjO),, a powder insoluble iu 
sodium hydroxide and melting at 62°. Accord- 
ing to Kurbatow, an oil boiling at 360° is obtained 
when the resin is subjected to destructive 
distillation. No umbelliferone is obtained (Som- 
mer, J. 1859, 573). 

The gum of olibanum behaves towards re- 
agents exactly as gum arable (Heckmeijer, J. 
1858, 482). 

Volatile oil of olibanum, examined by Sten- 



house (Annalen, 35, 306), boils at 179-4'', and 
has a sp.gr. of 0-866. This oil Kurbatow has 
succeeded in separating into a hydrocarbon 
C,oHi5 olibene, which boUs at 156°-158°, has the 
odour of turpentine, and the sp.gr. at 12° of 
0-863, and an oxidised oil boiling above 175°. 
Olibene is soluble in alcohol and ether, and gives 
a crystalline hydrochloride C]oHie,HCl, which 
melts at 127°. Wallaoh (Annalen, 252, 94) finds 
that olibene is identical with Icevopinene, and that 
dipentene is contained in the higher boiling 
fractions. At the present day olibanum is sel- 
dom employed in medicine. Jt is used almost 
exclusively in the preparation of incense. 

Opopanax. A bright orange-brown gum- 
resin occurring in hard nodular or earthy- 
looking lumps. It was used by Hippocrates, 
and several varieties were known to Theophras- 
tus and Dioscorides. It is said to be derived 
from the Opopanax Chironium (Koch), a native 
of Southern Europe. 

Opopanax consists essentially of resin, gum, 
and a little volatile oil. The. most recent 
examination of opopanax is that by Tschirch and 
Knitl (Arch. Pharm. 237, 256) who found a 
specimen from the Opopanax Chironium (Koch) 
to contain : resin soluble in ether 51-8, resin 
insoluble in ether 1-90, gum 33-8, volatile oil 
8-3, free ferulic acid 0-22, vanillin 0-0027, 
moisture 2-0, bassorin and plant remains 2-0 p.c. 
The resin soluble in ether is the ferulate of a 
resinotannol, and on hydrolysis ferulic acid and 
oporesinotannol are obtained. The latter is a 
light brown powder having the composition 
OijHi30,(OH). The resin of opopanax insoluble 
in ether consists of free oporesinotannol. The 
purified gum contained 3-53 p.c. of ash, and an 
arabic acid was prepared from it containing 
C 43-17, H 6-42 p.c From the volatile oil a 
product was obtained in needles, which melted 
at 133° -134° and had the composition 
C 66-6, H 2-7 p.c. This substance is named 
opondl. 

A sample of opopanax examined by Baur 
(Arch. Pharm. 233, 209) contained plant frag- 
ments which showed it to be derived from 
some member of the genus Balsamodendron, 
order Bureeracece, probably froifi B. Kafal {Com- 
miphora abyssinica (Engl.)]. It contained 19 
parts p.c. oif resin, 6-5 of ethereal oil, and 70 of 
gum, besides plant fragments. 

The resin of opopanax gives no umbelliferone 
when distilled. When fused with potash, 
Hlasiwetz and Barth found the resin to yield 
catechol, together with protooatechuic acid 
(Annalen, 139, 78). The substance formerly 
known by the name of opopanax was alto- 
gether difEerent in odour and appearance 
from the resin described above. It was 
probably derived from a Persian member of 
the VmbeUiferK (Powell, Economic Products of 
the Punjab, 1, 402 ; Fliick. a. Hanb. 327). This 
resin differs from the usual variety by jdelding 
umbelliferone on dry distillation, also the volatile 
oil obtained from it contains sulphur. 

Opopanax was highly esteemed in ancient 
medicine, but it has now gone entirely out 
of use. 

Sagapenum. This gum-resin, which, like 
galbanum and asafoetida, has been known from 
the earliest times, is now seldom met with. Its 
botanical origin is not known with certainty. 



GUMS. 



21 



Fluckigei and Hanbuiy(FIuck. a. Hanb. 324) de- 
sciibe sagapenum as consisting of a tough, softish 
mass of closely agglutinated tears. The tears are 
brownish, not milkwhite like asafoetida, and 
when broken do not acquire a pink tint, and 
are without alliaceous odour. The specimen of 
sagapenum examined by these observers con- 
tained no sulphur, but yielded umbelliferone. 
Seven out of the eight specimens examined by 
Hirschsohn (Pharm. Zeit. 1875, 225 ; Pharm. 
J. [iii.] 7, 771), however, containpd sulphur, 
and this character served to distinguish saga- 
penum from ammoniacum, galbanum, and 
opopanax. Umbelliferone was always obtained. 
Resorcinol is formed when sagapenum is fused 
with potash (Hlasiwetz and Earth, Annalen, 
139, 78), and styphnio acid by treatment with 
nitric acid (Boettgei and Will, ibid. 68, 269). 
When some specimens of sagapenum are im- 
mersed in hydrochloric acid (sp.gr. 1-13) they 
acquire a permanent blue colour, but others 
do not exhibit this behaviour. 

A specimen of sagapenum investigated by 
Hohepadel (Arch. Pharm. 233, 259) was found 
on examination of the plant fragments contained 
in the drug to have been obtained from the 
stems and fruits of a Persian species of Ferula, 
order Umbelliferse. It contained resin, 56-8 j 
volatile oil, 5-8 ; water, 3-6 ; gum, 23-3 ; and 
impurities, 10-6 p.c. The purified resin is 
yeilowish-brown, and melts at 74°-76° ; when 
hydrolysed by boiling with sulphuric acid it is 
decomposed into umbelliferone and eagareaino- 
tannol, a brown substance having the composi- 
tion CjjHjsOb. The 66-8 parts of purified 
resin contained 40 of sagaresinotannol, 15-7 of 
combined, and 0-ll-0'15 of free umbdliferone. 
The ethereal oil contains 9-7 p.c. of sulphur. 

Seanunony. Scammonie, Fr. ; Scammonium, 
Gcr. A purgative gum-resin derived from the 
Convolvvlua Scammonia (Linn.), a native of 
Greece, Asia Minor, Syria, and Southern 
Russia. 

The gum resin obtained by incision from the 
living root, and known as scammony or ' virgin 
scammony,' has been used medicinally for many 
centuries. The value of this drug depends on 
its resinous constituent, which, however, is 
now usually prepared by extracting the dried 
scammony root with alcohol, and precipitating 
the resin from the solution with water ; but the 
resin from both of these sources appears to have 
been displaced in the market, to a large extent, 
by the resin obtained from the root of Ipomoea 
orizabensia (Ledanois), commonly known as 
' Mexican scammony root,' and until lately 
these two resins have usually been considered to 
be chemically identical. 

An investigation of scammony root and 
scammony made by Power and Rogerson (Chem. 
Soc. Trans. 1912, 101, 398) shows that the 
resins obtained from the root by the methods of 
incision and extraction, although similar, are 
not identical, while both these resins differ 
very considerably from that obtained from the 
root of Ipomoea orizabensia, which has also been 
examined by Power and Bogerson {ibid. 101, 1). 
Both of these resins are exceedingly complex in 
character, but consist to a large extent of 
glucosides and methylpentosides of jalapinolio 
acid a.nd its methyl ester, and, whilst the methyl- 



pentose obtained by the hydrolysis of the resin 
of scammony root appears to be identical with 
rhamnose, that from the resin of Ipomoea 
orizabensia yields a crystalline tetra-acetyl 
derivative not hitherto described. The resin 
from the last-mentioned source also contains 
small proportions of hentriacontane and cetyl 
alcohol, which are not present in the resin from 
scammony root ; also, differences are observed 
in extracting with various solvents both the 
crude resins and the products of their alkaline 
hydrolysis. 

Jalapinolic acid Ci5H3o(OH)C02H was first 
obtained by Mayer (Annalen, 95, 149) from 
' jalapin,' the name given to that portion of the 
resin of Ipomoea orizabensia, which is soluble in 
ether. Jalapinolic acid, subsequently investi- 
gated by Corner (J. pr. Chem. [U.] 57, 448), 
has been studied by Power and Rogerson (I.e.). 
It forms silky needles, m.p. 67°-68°, and is 
slightly dextrorotatory. The methyl ester boils 
at 220° (20 mm.) and crystallises in laminae, 
which melt at 47''-48°. 

Earlier investigations of scammony resin 
were made by Johnston (Phil. Trans. 1840, ii. 
341); Keller (Annalen, 104, 63; 109, 209); 
Spirgatis (ibid. 116, 289) ; Kromer (Chem. 
Zentr, 1893, i. 310), who have assigned formulae 
to the resins obtained, but in view of their 
complexity, it is evident that they cannot be 
regarded as definite substances (<•/. Power and 
Rogerson, J. Amer. Chem. Soc. 32, 112). 

The sugars contained in scammony root and 
those obtained by hydrolysis of the resin and 
of ' jalapin ' have been investigated by Votooek 
(Zeitsch. Zuckerind. Bohm. 27, 257; 30, 20, 
117 ; Ber. 37, 3859, 4615) ; Requier (J. Pharm. 
Chim. [vi.] 20, 148, 213 ; [vi.] 22, 435, 492, 540). 
Eor assay of scammony resin, v. Guigues (j. 
Pharm. Chim. [vi.] 22, 241 ; Bull. Soc. ehim. 
[iv.l 3, 872). • A. S. 

GUMS. Gums are amorphous substances, 
composed of carbon, hydrogen, and oxygen, 
which are characterised by the property of either 
dissolving in water, or of taking up enough of 
that solvent to become glutinous and form a 
mucilage. They are either derived from plants 
by spontaneous exudation, or are extracted by 
means of solvents. The gum usually contains 
some inorganic matter and occasionally a small 
proportion of nitrogen (c/. Stevens, Amer. J. 
Pharm. 77, 255). For a long time, the gums 
were considered to be carbohydrates. It is now 
known, however, from the researches of O'Sulli- 
van on gum arable (Chem. Soc. Trans. 45, 41 ; 
57, 69), Gedda gum (■Slid. 69, 1029), and gum 
tragacanth (Md. 79, 1164), that the gums are 
acids of high molecular weight, composed of an 
acid nucleus to which is attached a number of 
residues of various hexoses, pentoses, and bioses 
by means of ethereal oxygen Unkings. 

The proportions of the sugars united to the 
nucleus acid to form the natural complex gum 
acid, and the proportions of the complex acids 
in the mixture that constitute the natural gum, 
appear to vary in different seasons, since investi- 
gations have shown that the properties of the 
gum of a given plant are not always the 
same. 

The finer gums are used in pharmacy in the 
preparation of emulsions and pastilles, and as a 



22 



GUMS. 



constituent of emollient medicines, whilst the 
commoner qualities are used in the arts as 
adhesive agents, in the finishing of doth, in the 
preparation of ink, of water colours, and in 
calico printing. 

Many drugs, known as gums in commerce 
and not included in this article, will be found by 
reference to Baisams or Gjim beshts. 

One of the most important factors in deter- 
mining the quality of a gum is the viscosity of 
the solution it forms with water, and as no 
standard method is yet in use the results re- 
corded by difierent investigators arc usually 
< not comparable. The simplest method - of 
determining the viscosity is to allow a quantity 
of the solution to flow by its own weight out 
of a tube, provided with a capillary orifice, and 
to note the time of flow. The results obtained 
by this method are of little value, since the 
pressure under which the liquid fldws varies 
continuously, but the method is still in use as 
affording a rough comparison of viscosities. 
For more accurate work, recourse may be had 
to the use of a viscometer, such as that described 
by OstwaJd (Physico-Chemical Measurements, 
162). 

In addition to the viscosity determination, 
it is generally necessary to ascertain the per- 
centage of moisture present in a Sample of gum, 
the acidity, the amount of ash, the colour, taste, 
odour, and character of the solution it forms 
with water. The amount of moisture present 
should be merely enough to prevent the gum 
being excessively friable ; as a rule it varies 
between 12 and 16 p.c. The ash should be 
merely that due to the bases combined with 
the natural gum acid and in good samples is 
generally about 3 p.c. The solution should be 
free from marked taste or odour and not very 
dark in colour. 

In the early part of the 19th century, a good 
many gums were known, and the work then 
done resulted in the description of the properties 
of a few gum substances to which the names 
haasorin, cerasin, and oraJtre were given ; and 
chemists, dominated by the idea that the number 
of organic compounds was only small, on investi- 
gating a gum, identified its constituents with 
one or more of these substances. It now 
appears that the number of gum compounds is 
very considerable, and it cannot be safely in- 
ferred that the arabin, or cerasin, &c., found in 
one gum, is the same substance as the compound, 
given the same name, found in another natural 
product. For further particulars, see Robinson 
(Brit. Assoc. Reports, 1906, 227'j and the Imperial 
Institute Bvdletin, 6, 29), from which much of 
the information embodied in this article has been 
obtained. 

AcAOA AND At.tjep Ghus. 

Acacia gum. Oum arabic ; Acacia gummi. 
Oomme arcAique, Fr. ; Ardbiachea gummi, Ger. 
Acacia gum is the erudation from the stems and 
branches of various species of acacia, notably 
the A. Senegal (WiUd.), which inhabit Africa 
from Senegambia in the West to Elordofan, 
Southern Nubia, and the region of the Atbara 
in the East (Bentl. a. Trim. 94; Hohnel, Pharm. 
J. [iii.] 18, 1089; Fliick. a. Hanb. 233). The drug 
has been known from the earliest times, having 



been an article of Egyptian commerce in the 
17th century B.C. 

The most esteemed variety is Picked Turiey 
or white Senaar gum. This gum, also known as 
Sudan or Kordofan gum, is collected from the 
grey barked acacia tree. Acacia Senegal (WiUd.), 
known locally as ' hashab. ' In Kordofan, the gum 
is obtained ooth from gardens of acacia trees 
which are private property and from wild trees. 
In the gardens, the gum is obtained by arti- 
ficially incising the trees soon after the end of 
the rainy season, the bark is removed in strips 
from the principal branches of all trees which 
are three years old or upwards; the strips 
should be 1 to 3 inches wide, according to the 
size of the branch, and 2 to 3 feet in length. 
The incision shoidd not penetrate into the 
wood, and a thin layer of the inner bark should 
be 1^. About 60 days afterwards, the first 
collection of gum is made, and after that "the 
gum is collected every fourth day until the rains 
recommence and new leaves appear ; at this 
stage the exudation ceases. The gum. obtained 
from the wild or uncultivated trees is slightly 
darker in colour and of less value than that 
derived from trees under cultivatioiL It 
exudes naturally from the wild trees and 
usually dries into pear-shaped pieces which vary 
in size, according to the length of time between 
successive collections. Young hashab trees, 
8 to 10 feet high and 6 to 8 inches in girth, will 
produce gum, and the limits of age for this 
purpose may be taken as 3 to 15 or 20 years ; 
probably trees of from 8 to 12 years old are the 
most productive. The gum consists of lumps of 
various sizes, sometimes as lar^ as a walnut, 
and of a white or nearly white colour. The 
unbroken masses are rounded in shape, and 
traversed by numerous minute fissures. They 
are brittle and break with a vitreous fracture, 
exposing a transparent and in the finer varieties 
quite colourless mterior. 

Suakln, Talca, or Talba gain is derived from 
the ' red ' and the-' white ' barked acacia trees, 
bothof which are varieties of ^cac>aiSfeya2(I)elile). 
It is collected chiefly in the forests of the Blue 
Kile. The red talha tree is more abundant than 
the white and consequently most of the talha gum 
is derived from that variety. The trees are said 
not to be barked or wounded by the colleotors, 
who gather the gum they find exuding. Talha 
gum is so brittle that commercial specimens 
have usually, for the most part, fallen to 
powder. The particles exhibit a great variety 
of colour. 

Senegal gum, collected in the French colony 
of Senegal, is obtained almost entirely from the 
same species of acacia which yields the Kordofan 
gum, but it is probable that the poorer qualities 
are procured from other species. The gum 
exudes naturally through fisSires produced by 
the rapid and unequal desiccation of the barks 
of the trees by the hot winds experienced 
immediately after the wet season, but in recent 
years incisions have been made. Senegal gum 
is much darker in colour than the Sudan gum, 
and the surface of the lumps is unbroken by 
cracks or fissures. It is chiefly imported into 
France. A considerable quantity of this is, 
however, exported to other European countries. 

Morocco, Mogador, or Brown Barbary gum 
is exported from Morocco. It is stated to be 



GUMS. 



obtained from Acacia arabica (WiUd.)> and 
Acacia gy,mmifera{'Wiild.), but according to some 
authorities, much of the gum no\r exported is 
merely Senegal oi Sudanese gum, brought to 
Moroooo by caravans from the interior. It 
consists of fight dusky brown tears or vermiform 
pieces ; they show numerous superficial fissures. 

Cape gum is the product of the Aeacia 
horrida (Willd.), a native of Cape Colony. Its 
colour is amber brown. 

Aden and East Indian gum is produced in 
Abyssinia and Somahland and is exported from 
the towns on the Somali coast principally to 
Aden and Bombay. Prom these two ports, it 
is reshipped to Surope as 'Aden gum' and 
' East Indian gum ' respectively. The source 
of the gum is not known with certainty but 
some of it is doubtless collected from Acacia 
abyssinicia (Hochst.) and Acacia glaucophyUa 
(Steud.), which are known to occur in those 
regions. It consists of tear-shaped masses, often 
as large as an egg, and of a pale amber or 
pinkish hue. The best qualities approach the 
better classes of Kordofan gums in appearance, 
solubility, and other characters, but these gums 
are usually darker in colour. 

Australian or Wattle gum, the i)roduct of 
several Australian species of Acacia known 
locally as ' Wattles,' occurs in large hard 
globular tear-like masses oi lumps, varying in 
colour from deep yellow to deep reddish-brown 
(v. Maiden, Phaim. J. [iii.] 20, 86 ; c/. Fluck. 
a. Hanb.). 

Gum arable is not much more soluble in hot 
than in cold water. In alcohol it is insoluble. 
The aqueous solution is precipitated by basic 
lead acetate, but not by neutral acetate. It is 
also thickened or rendered turbid by the addition 
of solutions of borates or ferric salts or alkaline 
silicates. Salts of mercury or silver have no 
action on the solution, neither is it coloured blue 
by iodine. Gum arable yields about 3 p.c. of ash, 
consisting of calcium magnesium and potas- 
sium carbonates. Por analytical distinctions 
between piire gum arabic and gums with which 
it may be associated, v. Hager (Zeitsch. anal. 
Cheni.Il,360;Pharm.Centh.I885,388);Schlosser 
(Chem. News, 20, 120) ; Eoussin (J. Pharm. Chim. 
[iv.] 7, 251) ; Elwood (Pharm. J. [iu.] 19, 339) ; 
Hefelmann (Zeitsch. ofientl. Chem. 11, 195) ; 
PaUadino (BuU. Soc. chim. [iii.] 9, 678) ; Vamva- 
kus (Ann. Chim. anal. 12, 12). Methods of 
valuation of gum arabic are given by Fromm 
(Zeitsch. anaL Chem. 40, 143) ; Dieterich (ibid, 
40, 408), and a method for detecting the presence 
of gelatin is given by Trillat (Compt. rend. 127, 
724). 

The chief constituent of gum arabic is 
Ardbin, Arabic acid, or Gummic acid, combined 
with calcium and also perhaps with magnesium 
and potassium. The crude acid is precipitated 
when alcohol is added to an aqueous solution of 
gum arabic previously acidified with hydro- 
chloric acid. By successively redissolving in 
water and reprecipitating, the product can be 
obtained pure. Arabic acid is amorphous, 
soluble in water and insoluble in alcohol. 
Heated to 100° it is converted into insoluble 
mda-arabic acid (Neubauer, J. 1864, 624 ; 
Annalen, 102, 106 ; Gelis, J. 1857, 496), or the 
same change may be effected by treatment with 
concentrated acid (Fremy, J. 1860, 603). Meta- 



arabic acid is readily changed back again to 
soluble arable acid by the action of alkalis. 
Heat of combustion, v. Stohmann (J. pr. Chem. 
[ii.] 31, 298). Action of light, v. Edeiiibid. 19, 

The constitution of arabin has been investi- 
gated_ by O'Sunivan {l.c.) who showed that it 
contains the acid nucleus, CssH^Og^, to which 
he gave the name \-arabinosic acid, but after- 
wards unfortunately called it arabic acid, the 
name already given to the naturally occurring 
gum_ acid, arabin, which is a compound of 
arabinosic acid with the sugar residues, arabinan 
and galactan, the termination * an ' indicating 
the anhydride of the corresponding sugar. On 
complete hydrolysis, arabin yields arabinose, 
galactose, and arabinosic (arabic) acid. 

When oxidised with ordinary nitrio acid, 
gum arabic yields oxalic, mucic, tartaric, and 
racemio acids (Guerin, Annalen, 4, 265 ; Liebig, 
ibid. 113, 4 ; KiUani, Ber. 15, 35 ; Homemann, 
J. 1863, 381 ; Maumene, Bull. Soc. chim. [iii.] 
9, 138; Be'champ, ibid, [iii.] 7, 687). The so- 
called nitro derivatives of arabin are, like those 
of starch and cellulose, nitrates (Bechamp, J. 
1860, 621 ; I.C.). Acetio anhydride also reacts 
forming acetyl derivatives (Schutzenberger and 
Naudin, Zeitsch. Chem. 1869, 265). 

Gums from various species of Acacia grown 
in known localities have been examined by 
Meininger (Arch. Pharm. 248, 171), 

Allied gums. The gum known in commerce 
as Oedda gum, in appearance very similar to the 
inferior kinds of gum arable, has also been 
examined by O'SuUivan. He found that it is a 
mixture of several gum acids, which are con- 
stituted of the radicles of galactose and of 
arabinose or arabinan, attached in considerable 
numbers to a nucleus acid to which the name 
geddic acid is given. Geddio acid is an iso- 
meride of arable acid, CjgHjgOj^. Chamal 
gum is obtained from Chile, where it is pro- 
duced by the Puza lanuginosa (Schult.). It is 
partly insoluble in water. Chagual gum has 
been investigated by Winterstein (Ber. 31, 
1571). Feronia or wood apple gum is derived 
from the Indian tree Feronia elephantum 
(Correa) [cf. Hiiok. a. Hanb. 239). Qhati gum 
is the name given in India to gum produced 
in India itself, as distinguished from East 
Indian gum of exotic origin. In European 
commerce, however, the name ' Ghatti ' or 
' Gatty ' is practically restricted to the partially 
soluble and viscous gum derived from Ano- 
geissus latifolia (Wall.) and certain other species. 
It is derived from various trees and no attempt 
is made to keep the products of the different 
species separate. The result of this is that the 
gum may differ considerably in properties. 
Hog or Doctor gum consists of reddish tears. It 
is derived from the Rhus Metopium (Linn.), o> 
perhaps the Moronobea grandifiora (Choisy), 
natives of South America. This gum is quite 
distinct from the Hogg or Kuteera gum of 
India (cf. Tragacanth). Plants containing gums 
similar to acacia (v. Gm. 15, 196). Para and 
other gums (Pharm. J. [iii.] 18, 623, 746. and 
1009). 

Teagacanth and Allied Gums. 
Tiagacanth. Tragacantha. Oomme adra- 
gante, Fr. ; Traganth, Ger. A gmnmy exudate 



24 



GUMS. 



consisting in part of altered cells obtained eithei 
spontaneously or by means of incisions from 
the stems of various species of Astiragdlus, some 
of which occur in South Western Europe, whUe 
others are found in Greece and Turkey. The 
largest number, however, are indigenous in the 
mountainous regions of Asia Minor, Syria, 
Armenia, Kurdistan, and Persia. The traga- 
canth of commerce is produced in the last- 
named countries. In July and August, the 
shrubs are stripped of their leaves and short 
longitudinal incisions or slits are made in the 
trunks. The gum flows out, and, drying spon- 
taneously, is ready for gathering in three or four 
days, a the weather is fine during the drying 
process, the ' white leaf ' form of gum is obtained 
which is the most prized variety: If, however, 
rain falls or the wind rises, particles of dust 
collect on the surface of the gum which thereby 
loses its whiteness and becomes the ' yellow 
leaf ' form, the second quality. The form of the 
pieces is determined by the shape of the in- 
cision ; longitudinal incisions produce ' leaf ' 
or flake tragacanth, punctures yield ' thread ' 
tragacanth, while irregular shaped incisions give 
knob-like masses, generally coloured, and of 
relatively low value. •Another form, known in 
Persia as ' Arrehbor,' exudes from branches 
which have been cut by a saw (Imp. Inst. Re- 
ports, 1909, No. 63). 

When tragacanth is treated with water, one 
part dissolves and the other swells up, absorbing 
water, to the extent of even fifty times the 
weight of the gum used, the whole forming a 
thick mucilage. This may be diffused through 
more water when, on filtering, a, soluble gum 
passes through, and there remains on the filter 
a sUmy non-adhesive mucilage, iassorin, traga- 
canthin, or adragarUhin. In presence of alkalis, 
the whole of the gum dissolves readily in water 
(Fliick. a. Hanb. 178 ; Sandersleben, Phytochem. 
Untfersuch. Leipzig, 1880, 90 ; Premy, J. 1860, 
604). On hydrolysis of three samples of white 
tragacanth, Widtsoe and ToUens (Ber. 33, 132) 
obtained fucose and arabinose, whilst fuoose 
and xylose were obtained from two samples of 
brown tragacanth. Five different samples of 
tragacanth examined by Helger and Dreyfus 
(Ber. 33, 1178) were found to contain 9-4 to 
16-4 p.c. of water ; 3-1 to 2-7 of ash, also 16-1 
to 22-4 p.c. of galactose (estimated as mucic 
acid) and 30 to 42 p.c. of arabinose (estimated as 
furfuraldehyde phenylhydrazone). A specimen 
of vermiceUi tragacanth contained 4 p.c. of 
cellulose and 3 p.c. of starch. The samples 
obtained by artificial incision contain the larger 
proportions of water and ash. 

Tragacanth gum, investigated by O'SuUivan, 
was found, like Gedda gum, to be a mixture of 
several gum acids. It can be separated into a 
group of acids which remain in solution in dilute 
alcohol, and an insoluble portion, for which the 
name hassorin is appropriated. The acids of 
the soluble group were found to be built up on 
a nucleus acid, very similar if not identical with 
geddio acid, by its union with galactose and 
arabinose residues. The constitution of the 
insoluble portion has not been completely 
worked out ; but it yields a nucleus acid of the 
formula O14HJ0O1J, to which the name hassoric 
acid is given, and also intermediate acids formed 
of bassoric acid united to the residues of 



xylose, and of a new pentose sugar, tragacan- 
those. 

Allied gums. Bassora, Kuteera, or Cara- 
mania gum, Hogg gum tragacanth, consists of 
yellow or brown waxy masses. It comes from 
Persia where it is said to be derived from 
almond and plum trees, and is employed in 
Smyrna in the adulteration of tragacanth (Fliick 
a.Hanb.). TheGochlospermumGossypium {H.C.), 
a small deciduous tree growing abundantly in 
India, furnishes a gum which occurs in irregular 
rounded translucent lumps of a pale bufl colour. 
The gum is sold in the Indian bazaars as a 
substitute for tragacanth, which it closely 
resembles. This gum has the property of 
slowly giving off acetic acid when exposed to 
moist air, a property also possessed by the gum 
of StercvZia urens (Roxb. ) (Gurbourt, Pharm. J. 15, 
57). A stable acid, gondic acid, CjsHjsOji, has 
been obtained from the gum of CocMos'permum 
Gossypium{i).C.)mthe same manner as the arable 
and geddic acids of O'SuUivan. On hydrolysis, 
the gum yields 18 p.c. of acetic acid, calculated 
on the dry and ash-free substance, and is thus 
an acetyl derivative. Xylose and a hexose are 
among the other products (Robinson, Chem. 
Soc. Trans. 89, 1496). Cashew gum is the 
exudation of the Anacardium occidentale 
(Linn.), a small tree indigenous to tropical 
America. Cherry tree gum behaves towards 
water in a similar manner to tragacanth. 
The insoluble portion consists of cerasin, 
combined with metals of the alkalis or 
alkaline earths (Fremy, J. 1860, 504). For 
hydrolysis of cherry tree gum, v. Hauers and 
Tollens (Ber. 36, 3306). Unseed, marshmaUow, 
and fleaseed gums closely resemble tragacanth 
(Schmidt, Annalen, 51, 50 ; Frank, J. pr. Chem. 
[ii.] 95, 494 ; Kirchner and Tollens, Annalen, 175, 
215; Hilger, Ber. 36, 3197). Persian gum 
{v. Pharm. J. [3] 20, 793) is of a hard glassy type 
and its solutions in water are intermediate in 
character between those of tragacanth and gum 
arable. The trade in this gum is considerable, 
but the commercial value is lower than that of 
either tragacanth or fine gum arable (Imp. Inst. 
Report). Wood gum has been extracted from 
various woods, straw, loofah, and similar 
materials. It resembles cherry tree gum. On 
hydrolysis it yields xylose, and in some oases 
arabinose (Th. Thomsen, J. pr. Chem. [ii.] 19, 
146 ; PoumarMe and Figuer, Annalen, 64, 338 ; 
J. Soc. Chem. Ind. 1890, 335; Wheeler and 
Tollens, Ber. 22, 1046 ; 23, 137 ; Annalen, 254, 
320 ; Allen and ToUens, ibid. 260, 289 ; Bader, 
Chem. Zeit. 19, 55 ; Johnson, Amer. Chem. J. 
18, 24 ; Browne" and Tollens, Ber. 35, 1457 ; 
Salkowski, Zeitsch. physiol. Chem. 34, 162). 

Otheb Gujis. 

Agar agar gum, Bengal isinglass gum, the 
dried jelly of seaweed, which, under the 
name of agar agar, is obtained from China, 
forms with water, is largely composed of the 
gum gelose (Payen, J. 1859, 562) or ■pararMn 
the latter being contained also in the carrot 
and the sugar beet (c/. sugar beet gum). Gelose is 
insoluble in cold water, alcohol, dilute acids, 
and alkalis. 1 part in 500 of boUing water 
forms a jelly on cooling (Horin, J. 1880, 1010 ; 
Forumbara, J. 1880, 1011 ; Bauer, J. pr. Chem. 



GUTTA PBRCHA. 



20 



[ii.] 30, 375) (». Agab Agab). Oalactin, a 
very similar gum to gelose, is found in the seeds 
of tlie LeguminoscB (Miintz, Bull. Soo. chim. 37, 
409). 

Amyloid gums. These are distinguished 
from most gums by being coloured blue by 
iodine. 'The more important are : Amyloid 
(distinct from that derived from cellulose), the 
soluble gum of the cotyledons of the tamarind 
and other plants ; Quince gum, which breaks up 
into cellulose, gum, and sugar when heated with 
dilute sulphuric acid ; and Salep gum, derived 
from the bulbs of orchids (Frank, J. pr. Chem. 
[ii.]95,479; Hilger, Ber. 36, 8197). 

Animal gum. A gummy substance having 
the composition C,aHj|,Oii„2H20 has been 
isolated from the secretions of the salivary 
glands, from the bra,m, pancreas, kidneys, and 
other parts of the body. It is unafltected by 
the digestive ferments but is converted into 
sugar by dilute acids. It reduces ammoniaoal 
silver nitrate solution with formation of a 
mirror. With water, it gelatinises, forming a 
muoUage. It is insoluble in alcohol and ether 
(Landwehr, Zeitsch. physiol. Chem. 8, 122 ; 9, 
367 ; 13, 122 ; Zeitsch. anal. Chem. 23, 601 ; 
24, 640 ; Pouohet, Compt. rend. 20, 21 ; Folin, 
Zeitsch. physiol. Chem. 23, 347). 

Fermentation gum. This gum, Dexlran or 
Viscose, which occurs in the unripe sugar beet 
(Soheibler, Wag. J. 1875, 790), is formed in the 
lactic fermentation of cane sugar by the action 
of the bacterium Streptococcus {Leuconostoc) 
mesenteroides (van Teighem, Jahresb. Agrik. 
Chem. 1879, 644 ; Be'champ, J. Th. 1881, 85 ; 
Briining, Annalen, 104, 197). Formed also in 
muoio fermentation (Nageli, J. pr. Chem. [ii.] 
17, 409). Dextran CjEijOg is amorphous, 
soluble in water and precipitated there- 
from as an elastic thread-lUie mass by alcohol. 
By treatment with dilute sulphuric acid, sugar 
is obtained, and when oxidised with nitric acid, 
oxalic but no mucic acid. 

Dextrin v. Dbxtbin. 

Gum from German yeast (v. Salkowski, Ber. 

27, 497, 925, 3325 ; Hessenland, Zeit. Vereins. 
Rubenzuoh-Ind., 1892, 671). 

Iceland moss gum. Two gums have been 
isolated from the jeUy of Iceland moss, Cetraria 
islandica (Acharius). The one, lichenin CjHioOj, 
is unafEeoted by iodine, while the other, iso- 
lichenin, is coloured blue by that reagent. 
Lichenin is a transparent brittle mass which 
dissolves in hot water, the solution gelatinising 
on cooling. It is soluble in solution of ammonio- 
CQpper sulphate ; combines with bases ; is 
converted by dilute acids into sugar ; oxicfised 
by nitric acid, it yields oxalic add, and it 
reacts with glacial acetic acid, forming triacetyl 
lichenin CjHjAoaOs (Kuop and Schnedermauu, 
Annalen, 55, 165; J. 1847-8, 831; Errera, 
Inaug. Dis. Brussels, 1882, 18 ; Mulder, Annalen, 

28, 279 ; Helger and- Buchner, Ber. 23, 461). 
tsoLichenin is soluble in water, and unlike 
lichenin forms no acetyl derivative, nor is it 
soluble in ammonio-copper sulphate solution 
(Berg, J. 1873, 848 ; Errera ; Honig, Monatsh. 
8, 452). 

The lichen, Evernia Prunaelri (Ach), contains 
a gum resembling lichenin, everniin CeHijO, 
(Studei Annalen, 131, 241). 



Irish moss gum. The Irish moss, Chrondus 
crispy^ (Linn.), contains a gum which is 
soluble in water, insoluble in ammonio-ooppei 
sulphate, is not coloured blue by iodine and 
yields mucic acid when oxidised with nitric acid 
(Blondeau, J. 1865, 669 ; Fliickiger and Ober- 
meyer, J. 1868, 805 ; Painter, Pharm. J. [iii.] 
18, 362). 

Steroulia gum, derived from various species 
of StercuUa {v. Maiden, Pharm. J. [iii.] 20, 381). 

Sugar beet gum. Several forms of gum have 
been separated from the juice of the sugar beet. 
Arabic or meta-arabic acid {cf. gum acacia), 
dextran {cf. fermentation gum), pararabin 
(Reichardt, Ber. 8, 808), and lasvulan (v. Lipp- 
mann, ibid. 14, 1509). Pararabin is a powder 
which forms a jeUy with water of quite a different 
appearance from that obtained with meta- 
arabin. It is soluble in dilute acid solutions 
from which alkalis or alcohol precipitate it. 
LsBvulan is a by-product in the extraction of 
crystaUisable sugar from beet sugar molasses. 
When anhydrous, it is insoluble in water, but 
in its hydrated form it dissolves readily. When 
oxidised by nitric acid it yields mucic acid, and 
heated with dilute sulphuric abid it is entirely 
converted into Isevulose. 

Wine gum {v. Be'champ, J. 1875, 987; 
Chancel, J. 1875, 987 ; Neubauer, Zeitsch. anal. , 
Chem. 15, 194). A. S. 

GUM ACACIA V. Gums. 

GUM AfflfflONIACUM v. Gum besins. 

GUM ARABIC v. Gums. 

GUM ASAFCETIDA v. Gum bbsins. 

GUM BENJAMIN v. Balsams. 

GUM BENZOIN v. Balsams. 

GUM, BRITISH, v. Dextrin. 

GUM ELASTIC v. Rubbbb. 

GUM GALBANUM v. Gum resins. 

GUM GAMBOGE v. Gum resins. 

GUM KINO V. Kino. 

GUM LAC or LAC RESIN v. Resins. 

GUM MYRRH v. Gum besins. 

GUM THUS V. Resins. 

GUMMIC ACID V. Gums. 

GUN COTTON v. Explosives. 

GUN METAL v. Tm. 

GUNPOWDER V. Explosives. 

GURHOFITE v. Dolomite. 

GURJUN BALSAM. Wood-oil v. Oleo- 

BESINS. 

GURJUNIC ACID v. Oleo-eesins. 

GUROLITE or GYROLITE v. Calcium 

GUTTA PERCHA is the product obtained 
by coagulating the latex of certain species of 
Palaquium and Payena, belonging to the natural 
order Sapotaceoe, which are natives of the Malay 
Peninsula and Archipelago. The name is 
derived from two Malay words : getah and 
percha or pertja. The word getah is applied to 
any exudation from a tree, whilst percha or 
pertja refers either to the local name of the tree 
which was erroneously thought at first to furnish 
the product, or to the Malay name for Sumatra 
' Pulau Percha.' 

The introduction of gutta percha into 
commerce dates from 1843, when specimens were 
forwarded to London independently by two 
doctors resident in Singapore, Dr. William 
Montgomerie and Dr. Jose D' Almeida, and the 
remarkable properties of the material at once 
attracted attention. In 1847 the principal tree 



20 



GUTTA PEROHA. 



yielding gutta peroha was described and named 
by Sir W. J. Hqoker, and in the same year Dr. 
Ernst Werner von Siemens employed the 
material for insulating underground telegraph 
wires. 

The principal trees yielding gutta peroha of 
the best quality are Falaquiwm Owtta, Burok, 
P. dblongifoUum, Burck, and P. borne^nse, Burok. 
P. oblongifolium is considered by some botanists 
to be only a variety of P. Outta ; the common 
name for both in the Malay peninsula is Taban. 
A number of other species oiPalaquium furnish 
gutta percha of second quality, the chief of these 
being P. dbovatum, King (Taban putih), P. Main- 
gayi. King and Gamble (Taban simpor), and P. 
oxleyanum, Pierre [Dichopais yiw««Zato,Hemsley), 
which is variously known as Taban sutra, Taban 
putih, and Taban chaier in different parts of the 
Malay peninsula. Payena Leerii (Hook, and 
Benth.); and P. Bavilandi (King & Gamble), 
furnish the white gutta percha known as Getab 
Eundek or soondie. 

There has been considerable confusion re- 
garding the botanical identity of the trees 
yielding gutta percha, which has been increased 
by the fact that the same native name is fre- 
quently applied to distinct species in difierent 
districts. 

Palctquium Gutta is a large forest tree which 
usually attains a height of about 60 feet and has 
a straight oylindricS trunk. Trees up to 150 
feet or more in height and 4 to 6 feet in diameter 
have been recorded. The tree is easily recog- 
nised by its leaves which are a beautiful coppery 
gold colour on the under surface and dark 
glossy green on the upper. They vary con- 
siderably in size, the leaves of mature trees 
being about 2 inches long, whereas those of 
young trees are much longer.. 

The geographical distribution of the trees 
which furnish gutta percha is curiously restricted, 
as they only occur naturally in a small area 
comprising the southern portion of the Malay 
peninsula, Sumatra, Banca, Borneo, Celebes, 
the Susu Islands, and the Philippines. The 
trees are not indigenous in Java but have been 
introduced and are now being cultivated there. 

The latex is contained in isolated sacs which 
occur chiefly in the inner layers of the bark and 
also in the leaves. On making incisions in the 
bark the latex exudes and quickly coagulates, 
so that only a small yield of gutta percha can be 
obtained at one tapping. In consequence of 
this fact the Malays have adopted the destructive 
method of felling the trees in order to collect the 
gutta peroha. The tree is cut down and incisions 
extending right round the trunk are made at 
intervals of 9 to 12 inches or even less. In the 
case of the best kinds of gutta percha, the latex 
exudes into the incisions where it quickly coagu- 
lates and in about half an hour can be rolled ofi 
on a stick or scraped off with a knife. The 
latex of the inferior varieties does not coagulate 
so rapidly; it is collected in vessels placed 
underneath the incisions and is afterwards 
coagulated by gentle heating. The gutta 
percha is subsequently boiled in water and 
made into blocks of various shapes. 

The amount of gutta percha obtained per 
tree by the native method has been very variously 
Ftated, but it seems probable that the average 
return from 15 to 20 year old trees is not above 



1^ ozs.. Large forest trees have, however, been 
known to yield over 2 lbs. of gutta percha and 
a tree 160 feet high, in the Philippines, is stated 
to have furnished 8| lbs. 

In view of the serious destruction of the 
trees which is involved in the native method of 
obtaining the gutta percha, attempts are now 
being made in Ferak and in Java to collect the 
product by tapping the standing trees. The 
average yield by this method is not yet definitely 
determined, but in Perak a tree 69 j^ inches in 
girth has yielded 1 lb. 3J ozs. of gutta percha in 
21 tappings extending over 6 weeks. Gutta 
percha is also being extracted by mechanical 
processes from the leaves of the trees. The 
older methods, involving the use of solvents, 
which were first employed for this purpose, have 
been abandoned, as it was found that the 
chemical treatment adversely affected the 
diirability of the gutta percha when exposed to 
air and Light. 

Gutta percha resembles rubber in consisting 
essentially of a hydrocarbon, having the formula 
(CioHig)„, associated with resinous substances. 
It differs widely, however, from rubber in its 
physical properties. At ordinary temperatures 
it is hard, very tenacious, and cannot be stretched 
like rubber. On immersion in hot water it 
becomes soft and plastic so that it can be 
readily moulded; on cooling, it retains the 
shape given to it when soft Jind becomes hard 
but not brittle. When heated in the air, gutta 
percha decomposes and then takes fire, burning 
with a luminous smoky flame and giving off a 
characteristic odour resembling that of burning 
rubber. When submitted to destructive dis- 
tillation, it yields a mixture of liquid hydro- 
carbons, including isoprene, similar to those 
obtained by the distillation of caoutchouc. 

Gutta percha is not affected by weak mineral 
acids, strong hydrochloric or acetic acids, or 
strong alkalis, but is readily attacked by strong 
nitric or sulphuric acid. It is partially soluble 
in ether, alcohol, acetone, and cold petroleum 
spirit, which dissolve the resin ; and completely 
soluble in carbon disulphide, chloroform, carbon 
tetrachloride, and hot petroleum spirit. 

The hydrocarbon present in gutta percha, 
known jis gutta, is the essential constituent and 
exhibits in an enhanced degree the characteristic 
properties of the product. When dissolved in 
chloroform and treated with chlorine, bromine, 
or iodine, gulta forms addition products, with 
some evolution of the halogen acid ; and by 
the action of nitrogen oxides, nitrosites resem- 
bling those obtained from caoutchouc are 
formed. 

Gutta percha slowly absorbs oxygen when 
exposed to air and light, and in the process the 
guita is converted into a brittle resin. Gutta 
peroha is, however, not energetically attacked 
by ozone like caoutchouc. Harries has shown 
that if gutta is dissolved in chloroform and 
treated with ozone, an ozonide CioHuO, is 
formed which, when decomposed by steam, gives 
a mixture of laevulic aldehyde and acid and 
IsBVulic aldehyde peroxide like the corre- 
sponding ozonide prepared from caoutchouc, 
but in different proportions. Harries concludes 
that the hydrocarbons of rubber and gutta 
peroha are identical, both being probably 1 ; 5 
dimethylcjrctoootadiene (Ber. 1905, 38, 3985). 



GUTTA PERCHA. 



27 



The resinous bodies associated \rith the 
gatta are oxygenated substances. They were 
separated by Payen in 1862 into two portions : 
(1) a crystaJline white resin, soluble in hot but 
insoluble in cold alcohol, which he named 
aWane; and (2) an amorphous yellow resin, 
soluble in cold alcohol, which he named fluavile. 
It seems probable from recent investigations 
that these substances are mixtures and not 
single compounds. In 1892 Oesterle dis- 
covered in gutta percha a fourth constituent, 
which he named gvitane and foimd to contain 
86-4 p.c. and H 120 p.c. Tor information 
on the composition and chemical properties of 
gutta percha see papers by Bams^, Chick, and 
Collingridge, and by Caspari in J. Soc. C3iem. 
Ind. 1902, 21, 1367 ; 1905, 24, 1274. 

In the analysis of crude gutta percha, it is 
customary to determine the moisture, the resin, 
the gutta, and the insoluble matter (dirt). The 
moisture is usually determined by heating a 



weighed quantity in an air or water oven, or 
in vacud, until no further loss in weight occurs ; 
sometimes the water given o£E is collected and 
weighed. The resins are determined by extrac- 
tion with hot acetone in a Soxhlet apparatus, 
or by ether or petroleum spirit in the cold ; the 
solvent is distilled o£E and the resin weighed. 
The residue left after removal of the resin is 
treated with chloroform which dissolves the 
gutta leaving the insoluble matter ; the latten 
is removed by filtration, washed with ckloroform,- 
diied, and weighed. The gutta may be weighed 
after distilling off the chloroform or it may be, 
precipitated from the chloroform solution by 
the addition of alcohol and then dried and 
weighed. 

The composition of several representative 
specimens of gutta percha, derived from trees 
belonging to a single species, which have been 
examined at the Imperial Institute and by Dr. 
Obach, is given in the following table : — 



Variety of gutta peiclia 


Botanical source 


Gutta 


Keain 


Dirt 


Moiatuie 


Ash 


Getah taban merah i 


Palaquium Gutta . 


70-6 


13-9 


0-7 


14-8 


0-95 






68-3 


13-4 


8-1 


10-2 


0-89 


Getah taban putih . 


Uncertain . 


35-6 


49'5 


7-4 


7-5 


0-72 


Getah taban chaier . 




620 


43-4 


3-4 


1-2 


1-61 


Getah simpor . 


Palaquium Maingayi . 


44-9 


45-6 


8-4 


1-2 


2-13 


Getah taban sutra= . 


Palaquium dblangifoUum 


84-3 


10-7 


3-7 


1-3 


— 


Getahsundek^ 


Payena Leerii 


43-9 


37-6 


5-1 


13-4 


"■■ 



The commercial brands of gutta percha vary 
very considerably in composition and quality.- 
They are usually designated by the names of 
the countries in which they are produced or of 
the ports from which they are shipped. Obach 
has classified the 12 principal brands into foui 
groups as follows : — 

I. First quality — ^genuine from P. Gvita or 
obhngifoUvm a.nA allied species: (1) Pahang from 
the Malay peninsula, (2) Bulongan red, and (3) 
Banjer red from Borneo ; 

IT. Second quality — Soondie from Payena 
spp. ; (4) Bagan gooUe soondie, (5) Goolie red 
Boondie, both from Borneo, and (6) Serapong 
goolie soondie from Sumatra ; 

III. Third quality — white, botanical source 
not definitely known : (7) Bulongan white, (8) 
Mixed white, (9) Banjer white, all from Borneo ; 

IV. Fourth quality — inixed and reboiled : 
(10) Sarawak mixed, (11) Fadang reboiled, and 
(12) Banca reboiled. 

Obach hasgiven the average results of 751 
analyses of these varieties, representing 2282 
tons of raw gutta percha {see Cantor Lectures on 
Gutta Percha, published by the Society of Arts, 
Appendix v. 90-92). The figures for the 
genuine varieties may be given for comparison 
with those recorded above : — 



_»• 


Quantity 

repre- 
sented by 
analyses 


Percentage composition 




Lota 


Tons 


Gutta 


Eesin 


Dirt 


Water 


Bulongan red 
Banjer red . 


93 
37 
91 


233 

60 

232 


67-0 
61-8 
40-7 


13-3 
18-2 
200 


11-5 
10-8 
17-4 


18-2 
19-2 
21-9 



The treatment which crude gutta percha 
undergoes in the factory previous to its technical 
use may be briefly described. The lumps, after 
slicing if necessary, are softened by immersion 
in hot water and are then freed from impurities 
by treatment in a washing machine with hot 
water. The washed gutta percha while still 
soft is forced by pressure through wire gauze in 
order to remove any solid impurities which have 
not been eliminated in the washing process. 
The strained product is usually rewashed and 
is then transferred to the masticator or kneading 
machine, where the mechanically enclosed water 
and air are eliminated and the material rendered 
homogeneous. It is afterwards passed through 
a rolling mill and formed into sheets from } to 
J inch thick, which are cut into convenient 
lengths and stored in cellars until required for 
use. If it is desired to mix various kinds of 
gutta percha in order to obtain a product of a 
required composition, or to incorporate pig- 
ments, &c., the operation is conducted by 
means of a mixing machine fitted with specially 
shaped roUers which can be heated by 
steam. 

In certain cases the crude gutta percha is 
washed with a hot 5 p.c. solution oi sodium 
hydroxide in order to improve the colour. After 
treatment in this way, the product must be 
thoroughly washed with water to remove all 
trace of alkali. 

The loss which results on cleaning raw gutta 
percha (i.e. the quantity of dirt and watej 
present) is considerable, usually amounting to 
from 30 to 40 p.c. and sometimes to as much as 
50 p.c. 

' Obtained by tapping standing trees. 
' Analyses by Br. Obach. 



GDTTA PERCHA. 



For some puiposes a very hard gutta percha 
is required, und this can be obtained by removing 
the resin from the ordinary material by ^extrac- 
tion with solvents. 

The physical and mechanical properties of 
gutta percha depend very largely on the propor- 
tions of gutta and resin present. Thus the 
temperature at which it softens ; the time re- 
quired to harden on cooling; the tensile 
strength; and the degree of elongation before 
brealang are all related to the value of the ratio 
gutta : resin. 

The electrical properties, i.e. the insulation 
resistance, the inductive capacity and the di- 
electric strength, depend principally on the 
nature of the gutta and on the amount of water 
present, and are afieoted very little by the 
removal of the resin. (For determinations of 
the electrical properties of gutta percha^ see 
Obach, l.c. 62-65.) 

Gutta percha is employed for a variety of 
purposes, the chief of which are the insulation of 
submarine cables, and the manufacture of the 
covers of golf balls. 

The amount of gutta percha which has been 
used in the cable industry tarma a very large 
percentage of the total consumption. It was 
stated by Obach that of the 71,933 tons of raw 
gutta percha used in the United Kingdom from 
1845 to 1896, at least two-thirds, and probably 
more, had been utilised for electrical purposes. 
The gutta percha employed for cable manu- 
facture has to be specially selected for thepurpose, 
as the insulating power of the different com- 
mercial brands varies enormously. 

The gutta percha used for the covers of golf 
balls is hardened ' by removal of the resin in 
order to render it as tough and elastic as possible. 

Gutta percha is also utilised for the manu- 
facture of driving belts ; rings, valves, &c., for 
pumps and hydraulic presses ; boot soles ; 
tubes, funnels, bottles, buckets, &c., for use 
with acid liquids ; for cements (such as Chatter- 
ton's compound) ; for taking casts ; and for 
surgical and many other minor purposes. 

H. B. 

GYNOGARDIN v. Glucosides. 

6YN0VAL V. SVHTHETIO drtigs. 

GYPSUM (Fr. Oypse; Ger. Gyps; Ital. 
Qesso). A common mineral composed of 
hydrated calcium sulphate CaS04,2HjO, cry- 
stallising in the monoclinio system. The name 
sdenite is sometimes applied to thp clear crystal- 
lised variety, satin-spar to the finely fibrous 
variety, and alabaster {q.v.) to a compact, marble- 
like variety used for carving. The low degree 
of hardness (No. 2 on the scale) is a very charac- 
teristic feature ; the mineral can be readily 
scratched with the finger-nail. Sp.gr. 2-32. The 
mineral is usually white, but sometimes greyish, 
yellowish, or reddish ; and the glistening 
cleavage surfaces are usually conspicuous on a 
broken surface. The crystsds possess a highly 
perfect cleavage in one direction parallel to the 
plane of symmetry ; on the smooth, bright 
cleavage surfaces the lustre is pearly, and 
coloured bands (Newton's rings) are often to be 
seen. Cleavage flakes are flexible but not 
elastic (thus differing from mica), and when 
bent d, fibrous cleavage is developed parallel 
to the faces of a pyramid : this fibrous cleavage 
is seen as sUky striations on the principal 



cleavage, and is a very characteristic feature of 
gypsum. 

Single crystals of gjrpsum, with a rhomb- 
shaped outline, are of common occurrence, em- 
bedded in clays. Fine groups of water-clear 
crystals are found in the sulphur mines of 
Sicily, the salt mines of Bex in Switzerland, and 
at many other localities. Enormous crystals, a 
yard in length, have been found in a cave in 
Wayne Co., Utah. Various types of twinned 
crystals are of common occurrence. The 
deposits of massive gypsum, such as are mined 
for economic purposes, occur as thick beds and 
nodular masses in sedimentary rocks of various 
geological periods. Those of the midlands of 
England are interbedded. with the red marls 
and sandstones of Triassio age; .those worked 
near Battle, in Sussex, belong to the later 
Purbeck beds ; many of the deposits of the 
United States are of Palseozoio (Siluriab, 
Devonian, and Carboniferous) age ; whilst the 
important deposits in the Paris basin are of 
Tertiary (Eocene and Oligocene) age. These 
more extensive deposits of gypsum have been 
formed by the evaporation of water in inland 
lakes and seas ; and they are often associated 
with beds of rock-salt. The mineral has, how- 
ever, in many cases originated by the action of 
water containing sulphuric acid and soluble 
sulphates (produced by the weathering of iron- 
pyrites and other sulphides) on limestone and 
other calcareous rocks. It is also formed by 
the action of volcanic vapours on the surround- 
ing rocks. 

The output of gypsum in England amounts 
to about a quarter of a million tons per annum ; 
about half of this amount is mined in Notting- 
hamshire, considerable quantities in Stafford- 
shire, Sussex, and Cumberland, and less in 
Derbyshire, Yorkshire, Westmoreland, and 
Somersetshjre. The value ranges from 6 to 10 
shillings per ton. In France, the output 
reaches IJ million tons per annum, and about 
the same amount is produced in the United 
States. Nova Scotia and New Brunswick are 
also large producers. The French gypsum, ia 
remarkable in containing some admixed calcium 
carbonate and soluble silicaj- and for this reason 
it makes a harder plaster. 

The principal use of gypsum is for the manu- 
facture of plaster of Paris, stucco, and various 
kinds of wall plaster. Hence the popular name 
'plaster-stone.' The employment of plaster of 
Paris for making the moulds in the potteries has 
given rise to the name ' potter's stone ' for gjrp- 
sum. The coarser grades of material are used 
as fertilizers (land plaster). Alabaster is used 
for carvings for inside decorations ; and satin- 
spar is cut as beads and other small personal 
ornaments. Under the names 'terra alba,' 
' annaline,' and ' satinite,' ground gypsum is 
used for adulterating pairits and as a mineral 
loading in the manufacture of paper (v. 
£!alcium). l. J. S. 

GYROPHORIC ACID C^HijO, is found in 
Vmhilicaria puatulaia (Hoffm.), Gyrophora vdlea 
[(linn.) Ach.], Gyrophora spodochroa [(Ehrh.) 
Ach.] and other lichens. It crystallises in 
needles from ether or dilute alcohol, 
melting at 202° with decomposition. Very 
easily soluble in acetone and alcohol. The 
alcoholic solution has an acid reaction, and gives 



HALOGEN ACETIC ACIDS. 



29 



a violet ooloui with ferric chloride. Is soluble 
iu alkali to a yellow solution ; boiling acetio acid 
converts it into orseUinio acid and boiling 
alcohol into oisellinio acid and its ethyl ester 



(Stenhouse, Annalen, 70, 218 ; Hesse, J. pr. 
Chem. [ii.l 58, 475 ; 62, 462 ; 63, 622 ; 68, 1 ; 
Zopf, Annalen, 300, 330; 313, 322; 317, 110; 
338,35} 340,276; 346,82). 



H 



HAARLEM BLUE. Anlwerplluev. Piqmbnts. 

HffiMATEIN V. Logwood. 

HJEMATIN V. Blood. 

HiEMATITE or HEMATITE. A mineral 
consisting of ferric oxide (FcaOj), crystallising in 
the ihoiabohedral system, and an important 
ore of iron (Fe, 70 p.c). According to whether 
it is crystaUised, massive, or earthy, it varies 
considerably in external appearance. In aU 
cases, however, the mineral gives a characteristic 
brownish-red streak or powder ; and it is on 
account of this colour (resembling that of dried 
blood) that the mineral receives its name hse- 
matite, meaning, in Greek, blood-stone. The 
sp.gr. of-the crystals is 6-2, but of the compact 
and earthy varieties it may be as low as 4-2 ; 
hardness 6 (except in the soft, earthy varieties). 

The crystals are iron-black with a briUiant 
metallic lustre, and they vary from rhombo- 
hedral to tabular iu habit. This variety is 
distinguished as iron-glance, or specular iron ; or, 
when the crystals are thin and scaly, as micaceous 
iron-ore. The compact varieties are distinguished 
as red iron-ore or red hcematite. These sometimes 
exhibit a fibrOus or columnar structure and a 
nodular surface, being then known as kidney- 
iron-ore; or, when the fibrous structure is so 
marked that the mineral breaks into rods, as 
pencil-ore. In these cases the material is often 
dark-red with a dull surface, but sometimes it 
may be iron-black with a sub-metallic to metallic 
lustre. Earthy, ochreous varieties are brighter 
red iu colour, and are often mixed with clay and 
other impurities ; these are known as reddle, 
ruddle, and red iron-froth. 

Hfflmatite occurs under a variety of condi- 
tions. The best crystals are found in connec- 
tion with metamorphio silicate rocks and in 
mineral- veins ; whilst the extensive masses of 
red iron-ore occur as bedded deposits in sedi- 
mentary rocks, often in association with lime- 
stone. The deposits on the east coast of the 
island of Elba, which have been extensively 
worked since the time of the Romans, consist 
of specular iron ; whilst those of west Cumber- 
land and north Lancashire, filling large irregular 
cavities in limestone, consist of red iion-ore and 
kidney-iron-ore. 

Besides being used as an ore of iron, hsema- 
tite, in its harder, compact varieties, is used, to 
a limited extent, as a gem-stone, and it was the 
material employed for some of the ancient 
Babylonian cylinder-seals. The pencil-ore of 
Cumberland is cut and polished for mounting on 
scarf-pins, &e., and for the burnishing tools 
used by jewellers and bookbinders. Ochreous 
varieties are used as a polishing material, and 
for making red paint and red pencils. 

L. J. S. 

HiGMATOGEN. A soluble iron albuminate. 

HiEMATOXYLIN v. Logwood. 



HEMOGLOBIN v. Blood. 

HAIDINGERITE v. Calcium. 

HALFA. Alfa, diva. Arabic name for Stipa 
tenacissima (Linn.); especially applied to the 
Esparto grass from Algeria. 

HALITE V. SoDiTTM chloride. 

HALLYOSITE. An uncrystallised clay- 
mineral with approximately the composition of 
kaolinite {q.v.) but containing rather more 
water (about 19 p.c). It forms compact masses 
wtih a slight greasy feel and lustre, and may be 
white, grey, or shades of various colours ; sp.gr. 
2-0-2-2 ; H. 1-2. It occurs as beds in sedimen- 
tary rocks and as masses in mineral-veins, and 
has sometimes been observed as a decomposi- 
tion product of granite and other rooks con- 
taining felspar. Possibly the minute amor- 
phous granules of china-clay and some other 
clays may be referable to this species. {See H. 
Ries, Clays, their Occurrence, Properties, and 
Uses, 2nd ed., 1908.) L. J. S. 

HALOGEN. A term originally applied by 
Berzelius to the group of non-oxygenated electro- 
negative radicles, simple and compound, which 
combine with metals to form salts known as 
haloid salts. Usually restricted to the four 
elements — Huorine, Chlorine, Bromine, and 
Iodine. 

HALOGEN ACETIC ACIDS. Derivatives of 
acetio acid in which the hydrogen of the methyl 
group is partly or whoUy replaced by a halogen. 

Chloeoacetio Acids. 

MoQOchloroacetic acid CH^Cl-COOH. Pre- 
pared by passing chlorine into acetio acid alone , 
(Hoffmann, Annalen, 102, 1), or in the presence 
of iodine (MiiUer, ibid. 133, 156), sulphur (Auger 
and B6hal, BuU. Soo. chim. [iii.] 2, 145), or red 
phosphorus (Russanow, J. Russ. Phys. Chem. 
Soc. 23, 222) ; by the action of chlorine on acetyl 
chloride lq the presence of iodine (Jazukowitsoh, 
Zeitsoh. Chem. 1868, 234) ; by the interaction 
of chlorine, glacial acetio acid, and acetic anhy- 
dride at 100° (Hentsohel, Ber. 1884, 17, 1286) ; 
together with acetyl chloride by the action of 
chJorine on acetic anhydride at 100° (Gal, 
Annalen, 122, 374) ; by the interaction of 
ethylene and chlorine peroxide (Fiirst, ibid. 
206, 78). 

Crystallises in two modifications, o- prisms, 
m.p.61-8°; (3-plates, m.p. 5601°. Byevaporat- 
ing an aqueous solution or by melting the solid 
substance, the j8- modification is produced ; this 
changes to the a- form on the addition of a 
crystal of the latter (Pickering, Chem. Soc. 
Trans. 1895, 665, 670; cf. ToUens, Ber. 1884, 
17, 665; Tanatar, J. Russ. Phys. Chem. Soc. 
24, 694); b.p. 185°-187°, 104°-105°/20 mm. 
(Sudborough and Lloyd, Chem. Soc. Trans. 
1899, 476) ; sp.gr. 1-3978 at 64-5° ; hydrates 
(Colles, Hid. 1906, 1252) ; heat of solution 



30 



HALOGEN ACETIC ACIDS. 



(Pickering, I.e. ; Lvginin, Ann. Chim. Phys. [v.] 
17, 251 ; Tanatar, I.e.) ; heat of combustion 
171-0 Calfl. (Berthelot, ibid, [vi.] 28, 567); 
electrical conductivity (Kortright, Amer. Qiem. 
J. 18, 368) ; magnetic rotation (Ferkin, Chem. 
See. "Trans. 1896, 1236) ; esteriflcation constant 
(Sudborough and Lloyd, I.e. ; cf. Lichty, Amer. 
Chem. J. 1895, 17, 27 ; 1896, 18, 690). Eeadily 
soluble in cold water, but on heating the solution 
decomposes into hydrochloric and ^ycollio acids 
(Buchanan, Ber. 1871, 4, 340, 863 ; Thomson, 
Annalen, 200, 75; Sevan, Proc. Camb. Phil. 
Soc. 1906, 13, 269 ; Senter, Chem. Soo. Trans. 
1907, 460). Metallic hydroxides of the type 
R'OH decompose it, yielding glycollio acid, 
whilst those of the type R"(0H)2 yield diglyooUic 
acid (Schreiber, J. pr. Chem. [ii.] 13, 346). By 
heating salts of chloroacetic acid with water in a 
sealed tube glycollic acid is produced (Kastle, 
Amer. Chem. J. 1892, 14, 686 ; Kastle and Keiser, 
ibid. 1893, 15, 471; cf. Euler, Ber. 1906, 39, 
2726). On distilling the acid in vacud with 
phosphorus pentozide, the anhydride 

(CHjaCOO),0 
is produced, whilst by distilling the acid through 
a heated tube, carbon monoxide, hydrogen 
chloride, <^»t-dichloromethyl ether and triozy- 
methylene are the products (Grassi-Cristaldi, 
Gazz. chim. ital. 27, ii. 602). On heating with 
4 parts of phosphorus pentachloride, it yields 
carbon tetrachloride and other products (Michael, 
J. pr. Chem. [ii.] 35, 96) ; with ammonia glycine' 
ia -produced. By ihteiaction with sodium 
sulphide and sulphur in alkaline solution a 
dithioglycollic acid ia produced, which on reduc- 
tion, yields thioglycollic acid (Kalle & Co. 
D. R. P. 180875; Chem. Soc. Abstr. 1907, i. 
1008). By the electrolysis of the potassium 
salt acetic acid, carbon dioxide and chlorine are 
formed, hydrogen not being evolved until the 
potassium salt is completely decomposed 
(Lassar Cohn, Annalen, 251, 335 ; cf. Bunge, J. 
Russ. Phys. Chem. Soo. 24, 690). By heating 
the dry silver salt, silver chloride and glycollide 
are produced (Beckurts and Otto, Ber. 1884, 14, 
676). The sodium salt or the ethyl ester react 
with potassium cyanide to yield the correspond- 
ing derivatives of cyanacetio acid (Phelps and 
Tmotson, Amer. J. Sci. 1908, [iv.] 26, 267, 275). 
For interaction with tertiary amines to yield 
beta!nes, v. Reitzenstein, Annalen, 1903, 326, 
305 ; with aniline, v. VaUfe, BuU. Soc. chim. 
1905, [iii.] 33, 966; with hydroxylamine, v. 
Rivals, Compt. rend. 1896, 122, 1489; with 
thiooyanio acid or its salts, v. Nencki, J. pr. 
Chem. [ii.] 16, 1 ; Jager, ibid. 17 ; with phenols, 
V. Saarbach, ibid. 21, 151 ; with nitrogen sulphide, 
V. Francis, Chem. Soc. Trans. 1905, 1839. 

Methyl eater. Prepared by passing chlorine 
into methyl acetate at 110°-120° (Censi, Bull. 
Soc. Ind. Mulhouse, 70, 311), and as ethyl ester 
(q.v.) ; b.p. 115° (Censi, I.e.), 130° at 740 mm. 
(Sohreiner, Annalen, 197, 8 ; cf. P. Meyer, Ber. 
1875, 8, 1152); sp.gr. 1-2352 at 19-2° (Henry, 
J. 1885, 1329). 

Ethyl ester. Prepared by the interaction of 
chloracetyl chloride and alcohol (WiUm, Anna- 
len, 102, 109), or by the action of alcohol on 
monochloroaoetic acid in the presence of sulphuric 
acid (Conrad, ibid. 188, 218) ; b.p. 144-5°-144-9° 
at 764-2 mm. ; sp.gr. 1-1585 at 20°/4° (Bruhl, 
ibid. 203, 209). Condensation products are , 



formed with ethyl sodiomalonate (Michael, Ber. 
1905, 33, 3217) ; benzylamine (Mason and 
Winder, Chem. Soo. Trans. 1894, 628) ; phenyl^ 
hydrazine (Reissert, Ber. 1895, 28, 1231 ; Busoh, 
Schneider and Walter, ibid. 1903, 36, 3877; 
MeussdorfEer, J. pr. Chem. 1907, [ii.] 75, 121) ; 
substituted ureas (Dixon, Chem. Soc. Trans. 
1897, 628) ; magnesium ethyl bromide (Svisskind, 
Ber. 1906, 39, 225) ; magnesium phenylamine 
iodide (Bodroux, Compt. rend. 1905, 140, 1597). 

Dichloroacetic acid CHas-COOH. Prepared 
by chlorinating acetic acid (Maumene, Annalen, 
133, 154 ; Miiller, ibid. 159) ; by the interaction 
of chloral and potassium cyanide (Wallach, Ber. 
1873, 6, 114 ; Annalen, 173, 295 ; Kotz, Chem. 
Soc. Abstr. 1910, i. 151) ; by passing chlorine into 
phloroglnoinol (Hlaziwetz, Annalen, 155, 132 ; 
Zincke and Kegel, Ber. 1889, 22, 1476) ; by the 
interaction of perchlorethylene and sodium 
ethoxide at 120° (Geuther and Fischer, J. 1864, 
316) ; of hexachlorotriketohexylene and water 
(Zincke and Kegel, I.e.) ; of pyrrol and sodium 
hypochlorite (Ciamician and Silber, Ber. 1885, 
18, 1764) ; of trichloroacetic acid and sodium 
or barium hydroxides (Pinner, ibid. 757) ; by 
hydrolysing the ethyl ester {q.v.). 

Colourless liquid, m.p. — 10-8° (Pickering, 
Chem. Soo. Trans. 1895, 667) ; b.p. 189°-191° ; 
sp.gr. 1-5724 at 13-5° ; mag.rot. (Perkin, ibid, 
1896, 1236) ; esterification constant (Sudborough 
and Lloyd, Chem. Soc. Trans. 1899, 476). 
Slowly decomposed by heating with water in a 
sealed tube at 100°, more rapidly with sodium or 
barium hydroxides {cf. Timof&ff, J. Rusa. Fhya. 
Chem. Eoc. 1904, 36, 255). By heating with 
silver oxide and a small quantity of water 
silver chloride and glyoxylic acid are produced 
(Beckurts and Otto, Ber. 1881, 14, 683). On 
electrolysis of an aqueous solution hydrogen, 
carbon monoxide, carbon dioxide, and an oil 
containing chlorine are produced (Troeger and 
Ewers, J. pr. Chem. [ii.] 58, 125). The potas- 
sium salt yields potassium chloride, . trichloro- 
acetic acid, and other products on dry distilla- 
tion (Friecbich, Annalen, 206, 244). Dichloro- 
acetic acid reacts with phosphorus pentachloride 
(Michael, Amer. Chem. J. 9, 215) ; aniline and 
its homologues (C!ech and Schwebel, Ber. 1877, 
10, 179; Heller, Annalen, 1904, 332, 247; 
1908,358,349; Ber. 1908, 41, 4264 ; Ostromiss- 
lensky, ibid. 1907, 40, 4972; 1908, 41, 3019; 
Heller and Aschkenasi, Aimalen, 1910, 376, 
261) ; thiourea (Dixon, Chem. Soc. Trans. 1893, 
816) ; nitrogen sulphide (Francis, ibid. 1905, 
1838). 

. Methyl ester, b.p. 142°-144° (Wallach, 
Annalen, 173, 299)'; sp.gr. 1-3808 at 19-2° 
(Henry, I.e.). 

Eihyl ester. Prepared by chlorinating alcohol 
(Altschul and Meyer, Ber. 1893, 26, 6767) ; By 
the interaction of chloral, alcohol, and potassium 
cyanide (Wallach, ibid. 1876, 9, 1212 ; 1877, 10, 
1526) ; or of dichlorinated vinyl ethers and 
alcohol (D. R. PP. 209268, 210502, 212592; 
Chem. Soo. Abstr. 1909, i. 453, 694, 873) ; b.p. 
167-7° at 754-6 mm. (SchifP, Annalen, 220, 108) ; 
sp.gr. 1-2821 at S0°/4° (Bruhl, ibid. 203, 22). 
With sodium or silver it 3delds maleic ester 
(Tanatar, Ber. 1879, 12, 1563). 

Trichloroacetic acid caa-COOH. Prepared 
■by chlorinating acetic acid in the sunlight 
(Dumas, Annalen, 32, 101) ; by the oxidation 



HALOGEN ACETIC ACIDS 



31 



of chloral with fuming nitrio aoid (Kolbe, ibid. 
64, 183; Clermont, Ann. Chim. Phys. [vi.] 6, 
135 ; Judson, Ber. 1870. 3, 782 ; Thurnlaokh, 
Annalen, 210, 63 ; Tommasi and Meldola, Chem. 
Soc. Trans. 1874, 314), ohromio aoid (Clermont, 
Compt. rend. 76, 774), or potassium permanga- 
nate (Clermont, ibid. 86, 1270). 

M.p. 67° (Sudborough and Lloyd, Chem. Soc. 
Trans. 1899, 476) ; sp.gr. 1-6298 at 60-6° ; heat 
of combustion (const, press. ) 92-8 Cals. (Berthelot, 
Ann. Chim. Phys. [vl.] 28, 569); electrical 
conductivity (Rivals, Compt. rend. 125, 274; 
Ostwald, Zeitsch. physikal. Chem. 1, 100 ; 3, 
177 ; Carrara, Gazz. chim. ital. 27, i. 207) ; 
esterification constant (Sudborough and Uoyd, 
l.c. ; ICailan, Monatsh. 1908, 29, 799) ; mag.rot. 
(Perkin, Chem. Soc. Trans. 1896, 1236). At 
300° it decomposes into triacetyl chloride, 
carbon dioxide, and hydrogen chloride (Engler 
and Steude, Ber. 1893, 26, 1443), whilst the 
silver salt yields the anhydride, silver chloride, 
carbon monoxide, and carbon dioxide (Beokurts 
and Otto, Ber. 1881, 14, 676) ; for sodium salt, 
cf. Henry, ibid. 1879, 12, 1844. At 200° with 
iodine tricUoride perohloromethane, hydrogen 
chloride, and carbon dioxide are produced 
(KrafEt, ibid. 1876, 9, 1049). Chloroform and 
carbon dioxide are produced by heating the acid 
with water or alkalis (Dumas, l.c. ; Otto, Ber. 
1871, 14, 589; Seubert, ibid. 1875, 18, 3342), 
potassium cyanide (Bourgoin, Compt. rend. 94, 
448), afiiline (Goldschmidt and Braiier, Ber. 
1906, 39, 109), tertiary bases ■ (Silberstein, ibid. 
1881, 17, 2664), antipyrine (Stoll6, Ber. Deut. 
pharm. Ges. 1910, 20, 371), or with resorcinol 
or cresol, but phenol or thymol yield hydrogen 
chloride, carbon monoxide, and phosgene 
(Anselmino, ibid. 16, 390). Reduction with 
potassium amalgam or hydriodio acid gives 
acetic acid. The sodium or zinc salt yields on 
electrolysis triohloromethy 1 trichloroacetate ( Elbs 
and Kratz, J. pr. Chem. [ji.] 55, 502). For 
compounds with aldehydes and ketones, v. 
Koboseff, J. Russ. Phys. Chem. Soc. 1903, 35, 
652; Plotnikoff, ibid. 1904, 36, 1088; 1905, 
37. 876 ; Ber. 1906, 39, 1794). 

Methyl ester. B.p. 152-3°-152-5° at 765-3 mm. 
(Schiff, Zeitsch. jhysikal. Chem. 1, 379 ; ef. 
Anschutz and Haslam. Annalen, 253, 124) ; 
sp.gr. 1-4892 at 19-2° (Henry, J. 1885, 1329). 

Ethyl ester. Prepared by the interaction of 
trichloroacetic acid and alcohol with sulphuric 
acid (Clermont, Compt. rend. 1901, 133, 737), 
or with hydrogen chloride (Spiegel, Ber. 1907, 
40, 1730) ; b.p. 164° ; sp.gr. 1-369 at 15° (Glaus, 
Annalen, 191. 68 ; Bruhl, ibid. 203, 22 ; Schiff, 
ibid. 220, 108). With ammonia it yields the 
amide; with sodium ethoxide, orthoformic ester, 
sodium ethyl carbonate, and sodium chloride are 
the products (Klein, Chem. Soc. Trans. 1877, 
i. 291. 

Bbomoaosiio Acids. 

Monobromoacetic acid CH^Br-COOH. Pre- 
pared by the action of bromine on acetic acid, 
either alone (Perldn and Duppa. Annalen, 108. 
106) or in the presence of carbon disulphide 
(Michael, Amer. Chem. J. 5, 202), or of sulphur 
(Genvresse, Bull. Soc. chim. [iii.] 7. 364) ; by 
the interaction of chloroacetio and hydrobromic 
acids at 150° (Demole, Ber. 1876, 561) ; by the 
oxidation of ethylene dibromide with fuming 
(ulphurb acjd (Kachler, Monatsb. 3, 559), or 



of monobromoacetylene in alcoholic solution by 
air (Glockner, Annalen, Suppl. 7, 11''). 

M.p, 49°-60° ; . b.p. 117°-118°/I5 mm. 
(Sudborough and Lloyd, Chem. Soc. Trans. 
1899, 477), 196° (Lassar-Cohu, Annalen, 251, 
342). On 1 eating an aqueous solution of the 
acid it is slowly decomposed into glycollio acid 
(Senter, Chem. Soc. Trans. 1909, 1828). Electrical 
conductivity (Ostwald, Zeitsch. physikal. Qiem. 
3, 178; Kortright, Amer. Chem. J. 18, 368). 
By heating the acid with silver powder at 130°, 
succinic acid is formed, whilst with silver nitrate 
silver glyoollate is produced (Senter, Chem. Soc. 
Trans. 1910, 346). Nitrogen sulphide yields 
bromoacetamide and bromodiacetamide (Fran- 
cis, ibid. 1905, 1839). The sodium salt heated 
in vacud yields glycollide. The potassium salt 
gives on electrolysis acetic acid, bromine, and 
carbon dioxide, no hydrogen being evolved until 
the potassium salt is completely decomposed 
(Lassar-Cohn, I.e.). Monobromoacetic acid has 
been used as a reagent for detecting albumin m 
urine (Boymond, J. Pharm. Chim. [v.] 20, 482). 

Methyl ester. Prepared by heating methyl 
alcohol and monobromoacetic acid in sealed 
tubes at 100° (Perkin and Duppa, Annalen, 
108, 109) ; b.p. 144°. 

Ethyl ester. Prepared as methyl ester, or 
together with other products by the interaction 
of sodium ethoxide and bromine (Sell and 
Salzmann, Ber. 1874, 7, 496); b.p. 159°. It 
undergoes numerpus condensations : with mag- 
nesium it yields ethyl acetoacetate and ethyl 7- 
bromoacetoacetate (StoUe, Ber. 1908, 41, 9a4) ; 
with ethyl oxalylacetate, ethyl citrate (Lawrence, 
Chem. Soc. Trans. 1897, 468); with ethyl 
Eodioacetoacetate, ethyl acetosuccinate (Sprank- 
ling, ibid. 1165) ; with ethyl dimethylacetoace- 
tate, ethyl aajS-trimethyl-jS-hydioxyglutarate 
(Perkin and Thorpe, ibid. 1178). 

For other esters, v. Clarke, ibid. 1910, 428 ; 
Steinlen, Bull. Acad. roy. Belg. [iii.] 34, 101 ; 
Kunckell and Scheven, Ber. 1898, 31. 172). 

Dibromoacetic acid CHBrj-COOH. Prepared 
by the action of bromine on acetic acid alone 
(Perkin and Duppa, Annalen, 110, 115), or in 
the presence of sulphur (Genvresse, Bull. Soc. 
chim. [iii.] 7, 478) ; by the hydrolysis of the 
ethyl ester (q.v.) ; m.p. 48° ; b.p. 232°-234° ; 
esterification constant, v. Sudborough and Uoyd, 
Chem. Soc. Trans. 1899, 477. The silver salt, 
heated with water, yields silver bromide, 
glyoxylio acid, and dibromoacetic acid (Perkin, 
ibid. 1877, i. 91). 

Ethyl ester. Prepared by the action of 
bromine on ethyl acetate at 160° ; by passing 
bromine into alcohol (SohafEer, Ber. 1871, 4, 
368) ; by the interaction of 4 parts of bromal 
hydrate with 1 part of alcoholic potassium 
cyanide (Remi, J. Russ. Phys. Chem. Soo, 7, 
263) ; b.p. 192°. 

TribromoaeetlB acid CBra-COOH. Prepared 
by the oxidation of bromal with fuming nitrio 
acid (SohafEer, Ber. 1871, 4, 370 ; Gal, Compt. 
rend. 77, 786) or by heating an aqueous solution 
of malonio aoid with bromine (Petriew, Ber. 
1875, 8, 730). Monoclinic plates, m.p. 131° 
(Sudborough and Lloyd, Chem. Soo. Trans. 
1899, 477 ; cf. Gal, Annalen, 129, 56) ; electrical 
conductivity, v. Swartz, Chem. Zentr. 1898, ii. 
703). On heating at 245° bromine and hydrogen 
bromide are evolved. By heating an aqueous 



32 



HALOGEN ACETIC ACIDS. 



solution of the acid or its salts, bromofoim is 
produced. For compounds with aldehydes and 
ketones, v. Kobosefi, J. Russ. Phys. CJhem. Soo. 
1903, 35. 652; Plotnikoff, ibid. 1908, 40, 64, 1238). 
Ethyl ester. Prepared by passing hydrogen 
chloride into a cooled alcohoUo solution of tri- 
bromoacetio acid (Broche, J. pr. Chem. [ii.] 60, 
98) ; b.p. 225°. 

Chlosobeomoaoetio Acids. 

CUorobromoaoeac acid CHCLBr-COOH. Pre- 
pared by heating monochloroacetio acid (1 mol.) 
mth bromine (1 mol.) in sealed tubes at 160° 
(Gech and Steiner, Ber. 1875, 8, 1174). Pungent 
liquid, b.p. 201°; ethyl ester, b.p. 160°-163°; 
amide, m.p. 126°. 

Monochloiodlbroinoacetic acid CClBr^-COOH. 
Prepared by heating monochlorodibromoacetal- 
dehyde with fuming nitric acid (Neumeister, 
Ber. 1882, 15, 603) ; rhombic plates, m.p. 89° ; 
b.p. 232°-234°, with decomposition. Potassium 
hydroxide converts it, on heating, into mouo- 
chlorodibromomethaue. 

Dichloromonobiomoacetic aeld CCljBr-COOH. 
Prepared by heating dichloromonobromoacetal- 
dehyde with fuming nitric acid (Neumeister, 
l.c.) ; prisma, m.p. 64° ; b.p. 215° with decompo- 
sition ; readily soluble in water or alcohol. 
Potassium hydroxide converts it, on heating, 
into dichloromonobromomethane. 

loDOACBTio Acids. 

Mono-iodoacetic acid CHjI-COOH. Prepared 
by decomposing the ethyl ester {q.v.) with baryta 
water (PerJdn and Duppa, Annalen, 112, 125) ; 
by heating acetic anhydride with iodine and 
iodic acid (Schiitzenberger, Zeitsch. Chem. 
1808, 484). Prismatic needles, m.p. 82°; 
electrical conductivity (Walden, Zeitsch. physi- 
kal. Chem. 1892, 10, 647) ; esterifioation constant 
(Sudborough and Lloyd, Chem. Soo. Trans. 
1899, 478). 

Methyl ester. Prepared in the same manner 
as the ethyl ester (Aronstein and Kramps, Ber. 
1881, 14, 604) ; b.p. 169°-171°. 

Ethyl ester. Prepared by the interaction of 
ethyl chloro- or bromoacetate, potassium iodide, 
and alcohol (Ferkin and Duppa, l.c.) ; together 
with other products by heating di-iodoacetylene 
with excess of alcoholic potassium hydroxide 
(Nef, Annalen, 298, 348). Colourless oil with a 
penetrating smell ; b.p. 69°/12 mm. ; 75°- 
78°/16 mm. (Tiemann, Ber. 1898, 31, 825). 

Di-iodoacetie acid CHIj-COGH. Prepared 
by the interaction of 1 part of malonio acid 
with 1 part of iodic acid in 4 parts of water ; 
carbon dioxide is evolved, the solution is cooled, 
filtered, and allowed to stand. After 2 or 3 
days crystals of tri-iodoacetic acid separate ; 
these are filtered off and, after heating the' 
filtrate, the di-iodo compound separates on 
cooling; m.p. 110° (Angeli, Ber. 1893, 26, 596). 

Ethyl erfer. Prepared by the interaction of 
ethyl dibromoacetate and potassium iodide in 
alcoholic solution (Perkin and Duppa, Annalen, 
1 1 7, 351 ), or of ethyl dichloroaoetate and calcium 
iodide (Spindler, ibid. 231, 273). Yellow liquid, 
which cannot be distilled unchanged under 
atmospheric pressure. 

Tii-iodoacetie acid Cla-COOH. For prepara- 
tion, V. di-iodoaoetic acid. Yellow plates, m.p. 
150° with decomposition. By heating with 



acetic acid iodoform and carbon dioTide are 
produced. 

HAMAMELIN. A preparation from the 
witch-hazel Hamamelis virginiana (Linn.), either 
green or brown in colour, depending upon 
whether the leaves or bark have been used. 

HARDWICKIA RESIN v. Oleo-rbsins. 

HABMALA. The seeds of the wild rue, Pe- 
ganum Harmala (Linn.), or harmal seeds, have 
been employed from the earliest times in Eastern 
medicine as a stimulant, anthelmintic, or even 
as a narcotic. They are said to be the source 
of a red dye produced in Southern Russia, and 
they have been used in the manufacture of oil. 
Wild rue is an odoriferous herbaceous plant, 
1-3 feet high, and inhabits Southern Europe, 
Asia Minor, Egypt, North-western India, and 
Southern Siberia (Muckiger, Pharm. J. [iii.] 2, 
229). 

Harmal seeds contain about 4 p.c. of two 
alkaloids (probably in combination with phos- 
phoric acid), which are found for the most part 
in the outer portions of the seed. The first of 
these, hammUne C,jHuNaO was discovered by 
Gobel (Annalen, 38, 363), the second, harmint 
OiaHjaNaO by Eritzsche (^id. 64, 360 j J. 
1847-8, 639; Annalen, 68, 351; 68, 355; 72, 
306 ; 88, 327 ; 88, 328 ; 92, 330 ; J. 1862, 377), 
who studied both alkaloids, and obtained 
numerous derivatives. Eritzsche extracts the 
seeds with water containing acetic or sulphuric 
acid, and saturates the solution obtained with 
common salt, which causes the alkaloids to 
precipitate in the form of hydrochlorides. The 
precipitate is dissolved in water, decolorised 
by treatment with animal charcoal, and the 
solution obtained is fractionally precipitated by 
ammonium hydroxide at 60°-60°. The fijcst 
portion of the precipitate is harmine, and the 
last portion harmaline. The crude harmaline is 
best purified by recrystaUisation from methyl 
alcohol (0. Fischer and Tauber, Ber. 18, 400). 
From methyl alcohol harmaline crystallises in 
small tables, or from ethyl alcohol in rhombic 
octahedra. It melts with decomposition at 238°. 
It is very slightly soluble in cold water or ether, 
but readily dissolves in hot alcohol. It forms a 
well-defined crystalline hydroMoride 
C,3H,.NaO,Ha,2HaO; 
Jiydrocyanide Ci3H,4N20,HCN; platinichloride 
(CisHnNjCHaJaPtCl, ; methiodide 

C,3HnN20,MeI; 
chromate (C, sHnNaO)2H jCrO, ; and nitro 
derivative C,aH,,(N02)N20. Both the hydro- 
cyanide and the nitro derivative , are bases, 
and combine with acids to form crystalline 
salts. Nascent hydrogen converts harmaline 
into a dikydride CiaHijNaO (0. Fischer, Ber. 
22, 638). Harmaline is shown by Fischer {ibid. 
28, 2481) to be dihydro- harmine, and it can be 
converted into harmine by oxidation, which ia 
best effected by potassium permanganate in 
dilute sulphuric acid solution. By oxidation 
with chromic acid in boiling acetic acid solution 
or by nitric acid both harmaline and harmine 
are converted into harminic acid CjoHgNaO,. 
By the action of hydrochloric acid on harmafine, 
Fischer and Tauber obtained a brick-red crystal- 
line powder harmalol C,aHiaNaO, which melts 
at 212° with decomposition. This compound 
also occurs naturally in harmal seeds, and has 



HELIUM. 



33 



been Isolated from these by Fischer (Chem. 
Zentr. 1901, i. 957). 

Haimine exists in harmal seeds in much 
smaller proportion than harmaline. It may,, 
however, be prepared from the latter by simple 
oxidation, either by the action of heat on the 
dry chromate, or by heating an alcoholic solu- 
tion of harmaiine nitrate to which hydrochloric 
acid has been added. Harmine crystallises in 
four-sided prisms (Schabus, J. 1864, 525). It 
melts with decomposition at 257''-259°. It is 
very slightly soluble itt^water or alcohol, and 
slightly soluble in ether. The salts of harmine 
are crystalline and colourless, and in acid solu- 
tion exhibit an indigo blue fluorescence. The 
more important are the hydrochloride 

Ci,HijNaO,HC!l,2H20 ; 

the platinichloride (C,8H,jN20,HC!l)2PtCl4; the 
methiodide C,sHijNaO,MeI (F.-and T.); and 
the two sulphates (OijH,jN20)2,H2S04,HjO, 
and CiaHijNjCHjSOi. Fritszche prepared the 
following halogen and nitro derivatives of 
harmine all of which are bases and form crystal- 
line salts : dichloroharmine CisHnjClaNaO ; 
nitrokarmine Ci8H,,(NOj)N20 ; cMoronitroluxr- 
niine C, ,Hi„Cl(NO j)N20 ; ■ and bromonitrohar- 
mine OijHioBr(NOa)NaO. A tetrabromide 

CiaHiaNaOBr/ 

has been obtained by Fischer. ^ 

When harmine is treated with concentrated 
hydrochloric ^cid at 140°, Fischer and Tauber 
find that it breaks up into methyl chloride and a 
new phenolic compound harmol CjaHioNjO, 
which crystallises in needles and melts at 321°. 
When harmol is fused -with potash it yields a 
compound possessing both basic and acid pro- 
perties, harmolic acid, CjaHjoNaOj, which melts 
at 247° (Fischer, Ber. 22, 637). Fischer ^nd 
Tauber, by acting on harmine in acetic acid so- 
lution with chromic acid, obtained dibasic har- 
minic acid CsHuNaCCOOH),. It forms silky 
needles, melting at 345°, at which point it de- 
composes into carbon dioxide and a crys- 
talline basic sublimate of apoharmine CnHjNa, 
m.p. 183°, from which Fischer obtained a well- 
defined gold salt. A tetrabromide CjHjNaBrj, 
and a dihydride OgHjNaHa, were also obtained. 
Other derivatives of harmine are described by 
Fischer and Buck (Ber. 38, 329). A. S. 

HARMALIN. Fuchsin v. Tbiphbnyl me- 
thane COLOUMNQ MATTEEa. 

HARMALINE, HARMALOL, HARMINE, 
HARMINIC ACID, HARMOL and HARMOLIC 
ACID, V. Haemala. 

HARTIN V. Resins. 

HARTITE V. Resins. 

HAUERITE. Manganese disulphide MnSj 
V. Manganese.. 

HAUSMANNITE. Trimanganic tetroxide 
MujOj {v. Manganese). 

HAZELINE. Trade name for a fragrant es- 
sence obtained from the fresh bark of Hama- 
metis virginiana (Linn.) or witch-hazel. Is 
probably analogous to eucalyptol. Is a colour- 
less oil, possessing a pleasant pungent smell and 
sweet astringent taste. Is used in the treatment 
of eczema, ulcers, burns, &c., and as a substitute 
for arnica. 

HEAVY SPAR. Native barium sulphate v. 
Barytes and Bamum. 
Vol. III.— r. 



HEBBAKHADE v. Gum besins. 
HECLA POWDER v. Explosives. 
HEDERIC ACID. An acid contained in ivy 
berries ; v. Ivy gum resin, art. Gum resins. 

HEDERINE. A poisonous glucoside 
OjiHioiOia found in ivy.' Dextrorotary [o]j, 
= 16-27°. By hydrolysis yields rhamnose and 
hederidine CajH,^©^ crystallising in rhombic 
prisms, m.p. 324°, and subliming without 
decomposition. Hederine acts as a powerful 
cathartic (Hondas, Compt. rend. 128, 1463 ; 
Joanin, ibid. 128, 1476). 

HEDERO-TANNIC ACID v. Gum resins. 
HEDGE-MUSTARD OIL. An oil manufac- 
tured from the so-oaUed hedge-mustard qb 
bank-cresses {Saphanv^ Baphanistrum [Linn.]) 
cultivated in Hungary, and used as a sub- 
stitute for rafie-seed oil. The oil is brought 
to the market either by itself or mixed with 
rape-seed oil, and is occasionally sold under 
this latter name. The sUiquous fruit of the 
plant mentioned bears little seeds which contain 
30-35 p.c. oil. This can be for the most part 
obtained by pressing. It has a dark olive-green 
colour, and an odour and taste very similar to 
rape-seed oil ; its density and faculty for saponi- 
fying with alkali is also nearly the same, so that 
it is difficult to recognise it in a mixture of the 
two oils. Valenta has tested the two oils as 
regards their behaviour with the usual reagents. 
On acting upon them with acids of different 
strength, such as sulphuric and nitric acids, a 
mixture of these, aqua regia, phosphoric acid, 
tec, as well as with oxidising mixtures, as potas- 
sium dichromate' and sulphuric acid, or concen- 
trated nitric acid saturated with nitric oxide, 
various colours are produced with both oils, by 
the shade and intensity of which they can be 
fairly readily distinguished. The following re- 
action is most characteristic for hedge-mustard 
oil ; about 5 grams of the oil are saponified with 
potassium hydroxide and spirit with warming, 
and the soap thus obtained is filtered from the 
unchanged oil, which is golden-yellow, and 
almost odourless and tasteless. On adding a 
large excess of hydiTOchloric acid to the concen- 
trated filtrate, it assumes a distinct green colour 
if a somewhat large portion of hedge-mustard 
oil be present (J. Soc. Chem. Ind. 11,. 181). 
HEDONAL V. Synthetic drugs. 
HELCOSOL. Bismuth pyrogaUate v. Bismuth, 
Organic compounds of; and Synthetic drugs. 
HELIANTHIC ACID CnHi fig. Anaoidfound 
in sunflower seeds (Ludwig and Kromayer, Arch. 
Pharm. [ii.] 99, 1286). 

HELIANTHIN v. Azo- coLOURmQ matters. 
HELIOCHRYSINd. Naphthalene colourino 
matters. 

HELIOTROPE v. Azo- colouring matters. 
HELIOTROPINE is a crystalline, volatile, 
poisonous alkaloid of bitter taste contained in 
Heliotropium Europeum (Linn.), and H. 
Peruvianum (Linn.) (Battandier', Re'pert de 
Pharm. 1876, 4, 648). The name is also 
applied to a perfume {v. Piperonal). 

HELIUM. Sym. He. At. wt. 3-99 (Watson). 
This element is the lightest member of the 
group of inert gases discovered by Rayleigh and 
Ramsay. Its place in the periodic classification 
is before lithium. . ,ooo 

History. — ^During the solar echpse of 18b8 
Janssen observed in the spectrum of the solar 



34 



HELIUM. 



chromo3pheie a line in the yellow, nearly 
coincident with the sodium lines D^ and D^, 
which was not attributable to any terrestrial 
substance. Lockyer.xind !E^ankland supposed it 
to be due to the presence in the sun of a new 
element to which they gave the name ' helium ' 
{ijXios, the sun). 

Helium was first obtained by HUlebrand, 
who found that the gas evolved from the 
mineral uraninite gave a fluted spectrum, 
by him attributed to nitrogen, but afterwards 
proved to be due to helium (BuU. U. S. Geo!. 
Survey, 1889, 78, 43). 

The discovery of terrestrial helium was made 
by Ramsay when searching for argon, &o., in 
the gases evolved from the mineral cleveite, and 
its presence in the atmosphere was first noticed 
by Kayser (Chem. News, 1895, 72, 89), who 
detected the helium line in the air-spectrum. 
Por a complete bibliography and account of the 
earlier investigations on heUum, see Bamsay, 
Ann. Chim. Phys. 1898, [vii.] 13. 

Occurrence. — It is now known that helium is 
very widely distributed, though it occurs only 
in minute quantities. It is present in air in the 
proportion of 0-000056 p.c. by weight or 000040 
p.c. by volume, i.e. about 1 volume of helium in 
250,000 vols, of air (Ramsay, Proc. Roy. Soc. 
1908, 80, A, 599). HeUum also occurs in many 
minerals, of which the chief are cleveite, trSgerite, 
uraninite, and fergusonite, and it has been 
detected in the gases of many mineral springs, 
e.g. Bath ; in those of the Pyrenees (Bouchard, 
Compt. rend. 121, 392); of TiVildbad (Kayser, 
Chem. Zeit. 19, 1649) ; and of Maizi&res, the gas 
from the latter containing 6-34 p.c. of helium 
(Moureux, Compt. rend. 121, 819). 

The gas obtained from minerals usually 
consists principally of helium with about 10 p.c. 
of nitrogen and smaller amounts of argon, &c. 
In view of the chemical inertness of helium it is 
of interest to know in what state it exists in 
minerals. Ramsay and Travers have found 
that, by the action of heat alone, almost exactly 
halt the total helium in the mineral is evolved, 
whilst by heating with sulphuric acid the whole 
is obtained. The evolution of gas is also in 
some cases accompanied by an evolution of 
heat, suggesting that the hehum is present as 
an endothermio compound (Proc. Roy. Soo. 
1898, 62, 325). Gray has investigated the 
conditions under which helium is liberated on 
grinding minerals, and finds that its evolution 
begins when the particles have a diameter of 
lOjti and attains- a practical limit when the 
diameter is 3/t, 28 p.c. of the helium content 
being then liberated. He concludes that the 
heliam is contained in a structure which is 
large compared with the molecular structure 
(Proc. Roy. Soc. 1909, 82, A, 301). 

Strutt has investigated the accumulation of 
helium in rooks in geological time (Proc. Roy. Soc. 
1908, 81, A, 272), and concludes that it is due to 
unknown favourable circumstances, as the rate 
of loss of helium from minerals under experi- 
mental conditions is much greater than the rate 
of production from radioactive emanations (v.i.) 
(Proc. Roy. Soc. 1909, 82, A, 166). 

Helium occurs in the natural gas of Kansas 
in varying amounts : 1-84 p.c. was found in the 
gas at Dexter, Cowley Co., Kansas (Cady and 
MoFarland, J. Amer. Chem. Soc. 1907, 29, 



1523). It has also been found occluded in 
meteoric iron (Ramsay and Travers, Proc. Roy. 
Soc. 60, 442). 

PreparcUion and puriJiccUion. — ^The prepara- 
tion of helium always involves its separation 
from a mixture with nitrogen, argon, krypton, 
&c. The mixed gases may be obtained by any 
of the following methods : — 

(1) From ' atmospheric ' nitrogen, by passing 
the gas over heated magnesium (Ramsay and 
Travers, Proc. Boy. Soc. 64, 183); or a heated 
mixture of magnesium and lime (Maquenne, 
Compt. rend. 121, 1147), when the nitrogen is 
absorbed and the inert gases can be collected. 

(2) By fractional (flstiUation of liquid air, 
according to the method of Ramsay and Travers 
(Phil. Trans. 1901, 197, 47). Olaudehas designed 
an apparatus for producing considerable quan- 
tities of the lighter constituents of the atmo- 
sphere (Compt. rend. 1908, 147, 624). 

(3) From certain mineral springs {v.s. ). (For 
methods of colleoting the gases see Travers' 
Study of Gases, chap, iv., and Proc. Roy. Soc. 
60, 442. ) The gases from King's well, Bath, con- 
tain 0-12 p.e. of helium by volume, and have 
been used as a source of the gas by Bayleigh 
(Proc. Roy. Soc. 1896, 59, 198), the OJ^gen and 
nitrogen being separated as from air. It is 
calculated that tms well produces about 1000 
litres of helium annually. 

(4) By heating certain minerals alone, or 
with dilute sulphuric acid or acid potassium 
sulphate. This is probably the best method of 
preparing helium, and may be carried out as 
follows : — 

The mineral in fine powder is introduced into 
a wide tube of hard glass or iron sealed at one 
end and coimected by a rubber joint with a 
manometer and a reservoir, in which the gas 
can be collected over mercury. The whole 
apparatus is completely evacuated and the tube 
slowly heated to redness. When, after some 
hours, the evolution of helium becomes very 
slow, the heating is stopped and the gas is pumped 
out of the reservoir (Travers' Gases, 111). 
Fusion with an equal weight of acid potassium 
sulphate in a hard glass tube gives a larger 
yield, but much frothing takes place, and a 
preferable method is to heat with dilute sulphuric 
acid in an evacuated flask (Travers, Proc. Roy. 
Soc. 1898, 64, 131). This is a comparatively 
cheap method of production as 1 gram of cleveite 
yields over 3-2 o.c. of helium, and a kHog. of the 
mineral can be obtained for £1. 

From the mixture of gases thus obtained pure 
helium may be isolated by one of the following 
processes : — 

Jacquerod and Perrot have found that quartz 
is permeable to helium at 1000°-1200° ; there- 
fore by surrounding a quartz tube with impure 
helium at that temperature and pumping away 
the gas from the interior it can be obtained free 
from nitrogen and other inert gases (Compt. 
rend. 1907, 144, 135). Watson has shown that 
this process is not practicable with some kinds 
of fused quartz (Chem. Soc. Trans. 1910, 812). 
Ramsay's method consists in introducing tho 
impure gas into a vacuous tube containing 
charcoal at the temperature of liquid air (Proc. 
Roy. Soo. 1905, A, 76, HI). Under these^iondi- 
tions all gases except helium and neon are 
completely condensed, and the vapour pressure 



HELIUM. 



35 



of neon is so much less than that of helium, that 
by systematic repetition of the process a perfectly 
pure product can be obtained (Watson, I.e.). 

Properties. — ^Helium has so far resisted all 
efforts to cause it to combine with other elements. 
It appears, however, to be absorbed to some 
extent by the finely divided platinum deposited 
on the walls of a vacuum tube with platinum 
electrodes by the continued passage of an electric 
discharge (Travers, Proc. Roy. Soo. 60, 449). 
This afiords a method of separating small 
amounts of helium and argon, as the latter is 
only slightly absorbed under these conditions. 
Cooke has found that zinc yapourised in helium 
has a vapour density 12 p.c. greater than when 
vapourised in nitrogen at the same tempera- 
ture (Zeitsch. physikal. Chem. 1906, 55, 537). 
This indicates some tendency toward combi- 
nation. 

There is possibly some connection between 
the chemical inertness of the gas and the fact 
that its molecules are monatomic as shown 
by determinations of the ratio of the specific 
heats. Behn and Geiger, using a modification 
of Kundts' method, have found the value 
CyO„=l-63, which agrees with that required 
by theory and found experimentally in the case 
of other monatomic gases, e.g. mercury (Ber. 
deut. phys. Ges. 1907, 5, 657). 

The following determinations of the density 
of helium have been made (0=16) : — 

Ramsay and Travers (Phil. Trans. 1901, 197, 47) 

D=l-98 
Olzewski (Ann. Physik. 1905, [iv.] 17, 997) 

D=200 

Schierloh D= 1-985 

Onnes (Leyden, Comm. 1908, No. 108) D=202 
Watson (Chem. Soo. Trans. 1910, 97, 827) 

D=l-997 

The molecular weight is taken as 3-99, and 
as the gas is monatomic this is also the atomic 
weight. 

The refractive index ■ of helium is about 
1-000035 for the whole of the visible spectrum, 
the dispersive power being very small (Scheel 
and Schmidt, Ber. deut. Phys. Ges. 1908, 6, 
207 ; Hermann, ibid. 1908, 6, 211, 246). The 
accurate value of /t for the I) lines is 1-00003500 
(Burton, Proc. Roy. Soc. 1908, A, 80, 390; 
Cuthbertson and MetcaU, ibid. 411). 

Helium is diamagnetic (Tanzler, Ann. 
Physik. 1907, [iv.] 24, 931). Its coefScient of 
solubility in water is less than that of hydrogen, 
being 0-0134 at 0° and 0-0138 at 20°, with a 
minimum at 10° (AntropofE, Proc. Roy. Soc. 
1910, 83, A, 474). Helium resembles hydrogen 
also in that the product of pressure and volume 
increases with the pressure, and it is therefore 
used in thermometry at low temperatures. 
. Iron, platinum, palladium, and platinum- 
iridium are all impervious to helium at tempera- 
tures up to 1500° (Dorn, Phys. Ztg. 7, 312). 
The spectrum of helium is characterised by the 
presence of a strong line, Dg, in the yellow 
(A.=5876), which has been shown to be double, 
and a bright-green line (\=5016). The colour 
of the glow given by the gas in a Pliicker's tube 
varies with the pressure, being yellow at 7 mm. 
and green at 1-2 mm. pressure, according to the 
strength of one or other of these lines. This 
phenomenon led Runge and Paschen to assume 



that helium consists of two components (Nature, 
1895, 52, 520). This idea has been disproved 
by subsequent experiments (Nature, 1897, 56, 
380). 

After many fruitless attempts helium was 
first liquefied by Onnes (Proc. K. Acad. Wetensoh. 
Amsterdam, 1909, 11, 168; Compt. rend. 147, 
421), who found that when cooled in solid 
hydrogen it gave the Joule-Kelvin effect on 
expansion through a small nozzle and could 
therefore be liquefied by the Linde process. 
From 200 litres of the gas he thus obtained 
over 60 c.c. of liquid helium in 3 hours. 

It is a colourless mobile liquid of density 
0-122, being thus the lightest liquid Itnown. It 
boils at 4-5° absolute, and has a critical tempera- 
ture about 5° absolute, with a critical pressure 
of 2-75 atmospheres. By the rapid evaporation 
of liquid helium a temperature below 2-5'' 
absolute has been reached (—270-5°), but there 
was no indication of the formation of the solid 
(Onnes, Proc. K. Acad. Wetensch. Amsterdam, 
1909, 12, 175). Liquid helium has a point of 
maximum density in the neighbourhood of 
2° absolute (Onnes, Communication from Phys. 
Lab. of Leyden, No. 119). 

A method has been described by Bordas 
(Compt. rend. 1908, 146, 628) for the detection 
of small amounts of helium by means of a 
Pliicker tube connected with a Dewar tube con- 
taining charcoal (Dewar, Proc. Roy. Soo. 1904, 
74, 127). 

Tschermak has suggested the use of a vacuum 
tube containing helium as a standard in spectro- 
scopy, and as a source of light in determining 
refractive indices, &o. (Chem. Soc. Abstr. 
1902, ii. 189). Collie has found that the 
spectrum of. helium is considerably modified by 
the presence of mercury vapour and recommends 
a heUum-mercury tube containing a trace of 
hydrogen as a standard in spectroscopy (Proc. 
Roy. Soc. 1902, 71, 25). 

Production of helium from radioactive elements. 
The gas evolved from a solution of radium 
bromide is a mixture of oxygen and hydrogen 
with a radioactive emanation, which can be 
obtained pure by condensation at a low tempera- 
ture. When volatilised into a closed space the 
emanation phosphoresces and gives a character- 
istic spectrum, but in the course of about four 
days the radioactivity disappears and the 
spectrum changes to that of helium (Ramsay 
and Soddy, Proc. Roy. Soc. 1903, 72, 204; 
1904, 73, 346). During this change the volume 
increases to three times that of the original 
emanation (Dewar and Curie, Compt. rend. 
1904, 138, 190; Indrikson, Physikal. Zeitsch. 
1904, 5, 214 ; Himstedt and Meyer, Ann. 
Physik. 1904, 16, 184). 

It is probable that helium is the final product 
of the disintegration of radium. The rate of 
production of helium is 0-37 cub. mm. per day 
from 70 mgm. of radium chloride, and agrtsfls 
with that calculated by Rutherford on the 
assumption that a-particles are helium atoms 
carrying two ionic charges (Dewar, Proc. Roy. 
Soo. 1908, 81, A, 280). 

Helium is also a product of the disintegration 
of actinium (Giesel, Ber. 1907, 40, 3011), and of 
thorium radioactivity (Strutt, Proc. Roy. Soc. 
1907, 80, A, 56). The rate of production in 
this case also supports the view that the «- 



30 



HELIUM. 



particle is identical with the helium atom 
(Soddy, Phil. Mag. 1908, [vi.] 16, 513 ; Physikal. 
Zeitsch. 1909, 10, 41). 

HELKOMEN. Trade name for a basic 
bismuth dibromohydroxynaphthoate. Yellow 
odouiless powder. Used as a substitute for 
iodoform. 

HELLEBOREIN, HELLEBORIN, HELLEBO- 
RESIN, HELLEBORETIN, v. Buck hellebobe 

KOOT. 

HELL-HOFFITE v. Explosives. 

HELMITOL. Trade name for a compound 
of hexamethylene tetramine (urotropine) and 
anhydromethylene citric acid {v. Synthbtio 
DBtros). 

HEMELLITHENOL v. Phbnol and its 

EOMOLOOTTES. 

HEMIPINIC ACIDS CioHi„Oe. n-EeiAipinic 
acid (3 : i-dimethoxyienzene-1 : 2-diQg,rioii;ylic acid) 
is a product of oxidation of narcbtine (Wohler, 
Annalen, 1844, 50, 17; Blythe, ibid. 43) ; of 
opianic acid (Beckett and Wright, J. 1876, 806); 
of berberine (Schmidt, Ber. 1883, 16, 2589); of 
corydaline (Dobbie and Lauder, Chem. Soc. 
Trans. 1894, 57 ; ibid. 1895, 18; ibid. 1897, 657; 
ibid. 1902, 146 ; Martindale, Arch. Pharm. 1898, 
236, 214) ; and of other alkaloids. It is pre- 
pared by boiling the oxide of opianic anhy- 
dride with potassium hydroxide. The solution 
is then acidified and extracted with ether 
(Goldschmidt, Monatsh. 1888, 9, 766). It 
crystallises with | and also with 2 molecules of 
water. 

Properties. — Both in the normal and the 
meta acids the m.p. varies with the rate of 
heating. When heated rapidly it has m.p. 
about 181° (Bobbie and Lauder, Chem. Soc. 
Trans. 1899, 678). It is sparin^y soluble in 
cold water, readily so in alcohol; the aqueous 
solution gives an orange-yellow precipitate with 
ferric chloride, and no precipitate with silver 
nitrate solution. When heated with ammonia 
it yields an imide C10H9NO4 (Kiihn, Bet. 1895, 
28, 809), the potassium SE^t of which when 
heated with ethyl iodide at 150° yields the 
characteristic liemipinethylimide ; m.p. 92°-96° 
(Goldschmidt and Ostersetzer, Monatsh. 1888, 
9, 762; liebermann, Ber. 1886, 19, 2282; 
Preund and Heim, ibid. 1890, 23, 2906). When 
treated with phosphorus pentachloride at 140° 
hemipinic acid yields the anhydride, which is 
also obtained by the action of equal volumes of 
methyl alcohol and concentrated sulphuric acid 
on the acid (Beckett and Wright, I.e. ; Wegschei- 
der, Monatsh. 1897, 18, 649). 

The anhydride CigHjOg forms brilliant 
needles; m.p. 166°-167°; It reacts with 
hydroxyquinol, forming dihydroxydimethoxi/ fluo- 
rescein (liebermann and WolbUng, Ber. 1902, 
36, 1782), and with resorcinol, forming di- 
methoxy fluorescein (Priedl, Weizmann, and 
Wyler, Cliem. Soc. Trans. 1907, 1584). 

Lagodzinski has synthesised alizarin from 
hemipinic acid by treating the latter with 
benzene in the presence of ^uminium chloride. 
The aluminium compound so formed is decom- 
posed with hydrochloric acid, and the resulting 
product CijHjjOe.HjO is dissolved in cold 
sulphuric acid and heated to 100°. The violet 
solution is poured on to ice and the mono-methyl 
ether of alizarin so obtained is decomposed with 
hydrogen iodide (Ber. 1895, 28, 1427). 



The nuthyl ester exists in 2 modifications; 
m.p. 121°-122° and 138° respeotivdy, the latter 
being the more stable form at ordinary tempera- 
ture (Wegsoheider, Monatsh. 1897, 18, 418, 689, 
629). 

Other esters (Wegscheider, I.e. ; Monatsh. 
1902, 23, 327, 381; Landau, Ber. 1898, 31, 
2090 ; Cahn-Speyer, Monatsh. 1907, 28, 803) ; a 
number of metallic salts (Salzer, Ber. 1897, 30, 
1102), and many other derivatives have been 
obtained (Goldschmidt, Monatsh. 1887, 8, 512 ; 
Mealen, Eec. trav. chim. 1896, 15, 282, 323 ; 
Glaus and Predagi, J. pr. Chem. 1897, [ii.] 66, 
171 ; Besterzycki and Fink, Ber. 1898, 31, 930 ; 
Wegscheider, J.c, and Monatsh. 1903,24, 376; 
Dobbie and Lauder, I.e., amongst others). 

Orf gentle nitration, hemipinic acid yields 
chiefly nitro derivatives, but on more energetic 
nitration 6 : 6-dinitro-2 : 3-dimethoxybenzoic acid 
is formed (Wegscheider, Monatsh. 1908, 29, 54, 
557 ; ibid. 1910, 31, 709). 

m-Eemipinic acid (4:5-dimethoxybenzene- 
2:3-dicarboxylic acid) is a product of the oxida- 
tion of papavarine (Goldschmidt, Monatsh. 1885, 
6, 380) ; of laudanin {ibid. 13, 695) ; and of 
corydio acid (Dobbie and Marsden, Chem. Soc. 
Trans. 1897, 664). It is also obtained by the 
oxidation of trimethylbiazilin (Gilbody, Perkin, 
and Yates, Chem. Soc. Trans. 1901, 1400 ; ibid. ' 
1902, 1045) ; of tetramethylhaematoxyUn {ibid. 
1061); and of 4 : 5-dimethoxy-o-toluio acid (Luff, 
Perkin, and Bobinson, ibid. 1910, 1136). It can 
be prepared according tothefollowingmethod: — 

6:6-Dimethoxy-l-hydrindone (3 grams) is 
boiled with nitric acid (1^ grams) and water 
(36c.c.). The clear yellow solution is neutralised ' 
with sodium carbonate, mixed with hydrochloric 
acid untQ the solution turns Congo paper blue, 
evaporated to dryness, the residue mixed with 
sand and extracted in a Soxhlet apparatus 
with ether. The ethereal solution is dned over 
anhydrous sodium sulphate, evaporated, and 
the residue dissolved in hot water, and after 
digestion with animal charcoal and filtration, the 
solution is allowed tb evaporate slowly in the 
air. It can also be obtained by the oxidation 
of iso-nitrosodimethoxyhydrindone with potas- 
sium permanganate, wluch gives an aJmost theo- 
retical yield (Perkin and Bobinson, Chem. Soc. 
Trans. 1907, 1083) and by heating aqueous dime- 
thoxycarboxybenzoyl formic acid (Perkin, ibid. 
1902, 1026; see also Perkin and Yates, «6»y. 242). 

m-Hemipinic acid crystallises with 1 and with 
2 molecules of water, has m.p. about 199° 
(Dobbie and Lauder), and is much less soluble in 
water than the normal acid. Its aqueous solution 
gives a cinnabar orange precipitate with ferric 
chloride and a white precipitate with silver 
nitrate. On heating it forms an anhydride, 
m.p. 175° ; when fused with potash it yields 
protocateehuic acid and carbon dioxide. When 
treated with nitric acid it gives dinitroveratrol, 
whilst on reduction it yields 4 : 6-dihydroxy- 
phthalic acid (Rossin, Monatsh. 1891, 12, 488). 
Its ethylimide has m.p. 228°-230°, and unlike that 
from the normal acid, it is very sparingly soluble 
in methyl alcohol The ethyl esters have been 
prepared by Rossin (i.c.). 

HEMISINE V. Synthbtio dbuqs. 

HEMLOCK. Spotted hemlock; Gonium. 
Orande eigvs, Fr. ; Sehierling, Ger. Hemlock, 
Conium maculaium (Linn.) (Bentl. and To 118) 



HEMP. 



37 



13 an erect biennial herbaceous plant which in- 
habits the temperate portions of Europe and 
Asia as well as of North and South America. 
It was the essential ingredient in the poison 
potion administered to condemned criminals by 
the Greeks, and from that period to the, present 
day it has been a well-known article of materia 
medica. The leaves gathered from wild British 
plants at the time when the fruit begins to form, 
and the fruits collected when fully developed, 
but before they have lost their green colour, are 
employed in medicine in this country (Brit. 
Pharm. ; Smith, Pharm. J. [ii.] 10, 489 ; Har- 
ley, ibid, [iii.] 1, 584). The root possesses little 
01 no activity (Lepage, J. Pharm. Chim. [v.] 
6, 10). The action of hemlock on the system is 
that of a sedative to the motor nerves (Christi- 
son, J. Pharm. Chim. 22, 413 ; Hofmann, Ber. 
14, 705; Kuhlmann, Arch. Pharm. [ii.] 23, 
38), to which end the leaves are administered, 
preferably as juice or soUd extract, and the fruits 
in the form of tincture. For further botanical 
and historical particulars, and the mode of de- 
tecting the accidental admixture of allied um- 
belliferous plants V. Fliick. a. Hanb. 299-302. 

The physiological activity of both the leaves 
and fruit of hemlock depends upon the presence 
of the strong-smelling volatile liquid alkaloid 
coniine, amine, conkine, or circviine CjHjjN, 
together with smaller proportions of four nearly- 
related bases, methyl conine, conhydrine, \J>- 
conhydrine, 7-coniceine (Geisecke, Brandes Arch. 
Pharm. 20, 97 ; Geiger, Berz. J. 12, 220 ; Planta 
and Keknl^, AJinalen, 89,^ 129 ; Wertheim, ^id. 
100, 328; 123, 157; Ladenburg and Adam, 
Ber. 24, 1161; Wolffenstein, Md. 28, 302). 
Coniine has been prepared synthetically by 
Ladenburg (Ber. 19, 2579 ; 22, 1403) and proved 

CHj-CHj-NH 
to be dexlro-fa) propylpiperidine • 

CHj-CHa-CHPr. 
For properties and reactions v. Vegeto-alka- 
LOlDS. When hemlock leaves or fruit are tritu- 
rated with an alkali a strong odour is given oS, 
due to coniine and the other bases, with some 
ammonia, and by distUling such a mixture, 
using suitable precautions, the alkaloids are 
obtained. Geiger, for instance, distils the fruit 
with potassium carbonate or calcium hydroxide, 
and then by a series of operations separates the 
bases from the distillate. Christison distils in a 
similar way an alcoholic extract. Wertheim 
extracts with water acidulated with sulphuric 
acid, supersaturates the extract with lime or 
potash, and distils. The distillate is then 
neutralised with sulphuric acid, evaporated to a 
syrup, and treated with alcohol, which dissolves 
the alkaloidal sulphates, and leaves the ammo- 
nium salt, which is insoluble in that liquid. The 
alcohol is then removed by distillation, the 
residue supersaturated with potash, and ex- 
tracted with ether. The ethereal solution is 
distilled. After the ether has come' over, the 
distillation is conducted in a stream of hydrogen, 
when the first portions of the distillate contain 
the coniine, which may be purified by conver- 
sion into hydrochloride, reorystallisation, and 
regeneration by means of an alkali. Another 
method of isolating the alkaloids from the fruit 
is to extract with dilute acetic acid, evaporate 
the solution to a syrup in a vacuum, mix with 
excess of magnesia and extract with ether 



(Sohorm, Ber. 14, 1766). V. Braun (Ber. 38,3108) 
gives a method for the separation of the other 
bases present in the mixture of alkaloids remain- 
ing after the greater part of the conine has been 
removed Jby distillation. The percentage of 
alkaloids obtained varies, 0-2 p.c.of coniine being 
a good yield from the fruit. 

Conhydrine, which is much less active physio- 
logically than coniine, melts at 120-6°, and boils 
at 224-5° (719-8 mm.) (Wertheim, J. 1863, 435). 
Treated with phosphorus pentoxide or con- 
centrated hydrochloric acid it loses the elements 
of water, and is converted into the two iso- 
merides (o) and (;8) coniceXn CjHijN (Hofmann, 
Ber. 18, 7 ; Lellmann and Muller, ibid. 23, 680). 
y-Coniceine, discovered in impure conine by 
Wolffenstein, had been prepared previously by 
Hofmann (Ber. 18, 112) by treating bromconine 
with dilute caustic soda solution. It is a liquid, 
b.p. 173°, and has the same odoui as conine. 
i((-Conhydrine CsHijNO has m.p. 100°-102°, and 
b.p. 229°-231°. For estimation of the alkaloids 
in hemlock i>. Cripps (Pharm. J. [iii.] 18, 12 andSll) 
and Kremel (Ph. Post. 20, 521). Hofmann (Ber. 
17, 1922) discovered caff€io or dihydoxycinnamic 
acid C8H3(0H)2CH:CH-C00H in hemlock. It 
contains also a volatile oil, said to be the product 
of fermentation (Landerer, Bep. Pharm. 94, 237) 
and the leaves yield on ignition 12-8 p.c. of ash 
(Wrightson, Pharm. J. 5, 40). A. S. 

HEMLOCK SPRUCE RESIN v. BEsms. 

HEMP. The name of various plants and of 
the fibres derived from them (see also Bast- 
riBBES ). The following list embraces these fibres 
under their commercial denominations, with the 
names of the plants which produce them : — 

Common hemp . . Cannabis saliva 

, (Linn.). 

African bowstring hemp . Sansevzeriaguineensis 
(Willd. ) and others. 
Bastard hemp . . Datisca cannabina 

(Linn.). 
Bengal or Bombay hemp . Crotalaria juncea 

(Linn.). 
Bombay hemp (also) . Eibiscus canndhinus. 
Bowstring (of India) hemp Sansevieria Box- 

burgJiiiund others. 
Bowstring (of India) hem^\Calotropis gigantea 

(also) / (Dryaiid.). 

Brown hemp . . . Crotalaria juncea 

(Linn. ). 
Brown (Indian) hemyXEibiscus canna- 

(also) / hinus (Linn.). 

Florida bowstring hemp . Sansevierialongiflora 

(Sims). 
Indian (in America) hemp ." Apocynum eanna 

binum (Linn.). 
Jubbalpore hemp , . Crotalaria juncea 

(Linn.). 
Madras hemp . . . Crotalaria juncea 

(Linn.). 
Manilla hemp . . . Musa textilis. 
Sisal hemp . . . Agave rigida CiiiH.). 
Sunn hemp . . . Crotalaria juncea 

(Linn.). 
Virginian or Water hemp . Acnida cannahina 

(Linn. ). 

Of these, Cannabis sativa, nat. ord. Vrti- 
cacese, allied to the hop plant, furnishes the 
true hemp. The plant is an annual, growing 
ordinarily to the height of 8 or 10 feet, but 



38 



HEMP. 



sometimes exceeding that limit by several feet ; 
and it doubtless owes its origin to some part of 
temperate Asia. On extending its habitat, the 
character of the plant changed with soil and 
climate, giving origin to the supposed varieties 
G. chinensis and C. indica, the former of which 
is cultivated for its bast-fibres (hemp), while the 
latter is grown for its narcotics. 

Hemp fibre examined by the microscope re- 
sembles that of flax in being round and ribbed ; 
it has a mean diameter of 0-2 mm., and exhibits 
small, hairy appendages at the joints. Accord- 
ing to Haberlandt, the breaking strain of a cord 
of 1 sq. mm. section is on the average 34-5 kilos. 
In Manilla hemp the fibrous bundles are oval, 
nearly opaque, and surrounded by a number of 
rectangular cells composing a dried tissue. The 
bundles ate smooth. Sisal hemp forms oval 
fibrous bundles surrounded by cellular tissue ; a 
few smooth ultimate fibres projecting from the 
bundles. It is more translucent than Manilla, 
and is (Characterised by the large quantity of 
-spiral fibres in the bundle. 

Heinp is cultivated (1) for its fibre ; (2) for 
its resin ; (3) for the oil contained in its seed ; 
(4) for the seed itself. The tough, elastic, and 
durable fibre is better adapted for the manufac- 
ture of cordage and sail-cloth than any other 
known material. It is, moreover, employed for 
canvas, tarpaulin, and towelling. The finest 
qualities for these purposes are imported from 
Italy and Russia. The preparation of the fibre 
is similar to that of flax ; the stems being bruised 
and ' retted ' or fermented in water, after which 
they are again beaten out and fluaUy ' scutched ' 
and ' hackled ' or combed (v. Flax). The water 
in which hemp has been steeped produces no 
evil effects on the health of a district when 
allowed to flow into running water, but it always 
destroys the fish together with certain vegetable 
growths (Eenouard, Bied. Zentr. 1880). 

The resin of hemp is employed in India as 
charas, bhang or siddJii, and gdnjd, in which 
form it is used for its intoxicating and narcotic 
properties. Charas is the resin itself ; bhang 
or siddhi consists of the dried resinous leaves and 
stalks ; it is used for smoking, for making sweet- 
meats along with honey and sugar, or for form- 
ing a potable infusion. Odnjd is composed of 
\, the resinous fruiting heads of the female plant 
and is similarly employed. In 'A Report on 
Indian Fibres and Fibrous Substances,' Spon, 
1887, it is stated that Cannabis sativa (var. 
indica) is chiefly, if not exclusively, cultivated 
on account of its narcotic principle. It has 
been found that the narcotic-yielding plant 
affords only a worthless fibre, and it is presumed 
that the climate of India favours the production 
of narcotic at the expense of the fibre. To 
attempt an extension of its cultivation, fiscal 
difficulties of a very formidable character would 
also have to be overcome, for the Government 
of India would never permit a plant of which 
the leaves and flowers yield so pernicious a 
narcotic to be widely grown. According to 
Hunter (The Indian Empire, and its People, 
History, and Products, 2nd ed. 455), excise 
duties are levied upon these resinous products ; 
the hemp which furnishes them is omefly con- 
fined to a limited area in Rijshihi district, 
Bengal, and to the inner valleys of the Hima- 
layas. The use of them is a frequent cause, not 



only of crime, but also of insanity. Government 
attempts to check consumption — first, by fixing 
the retail duty at the highest rate that will not 
encourage smuggling ; and secondly, by continu- 
ally raising that rate as experience allows. 

T^ effect of hemp-resin and its compounds 
on the consumer is at first to exhilarate and to 
promote appetite. Further doses produce de- 
lirium, sleep, and sometimes catalepsy. 

Hemp-resin examined by T. and H. Smith is 
soluble in alcohol, and has a warm, bitter, acrid 
taste with a slight odour. It melts between 70° 
and 90°, and has a pale-brown colour. It is 
called cannabin. 

The oil is obtained by expression from the 
seed, which yields from 25 to 30 p.c. of oil, and 
70-75 p.c. of residual cake used for cattle feed- 
ing, although sparingly on account of its laxative 
properties. This oil has a sp.gr. of 0-9307. 

The essential oil of G. sativa was prepared 
by L. Valenta (Gazzetta, 10, 479-481) by dis- 
tilling the fresh leaves with water and agitating 
the resulting milky distillate with ether. The 
oil dried over calcium chloride and distilled 
repeatedly from sodium is colourless and mobile 
(b.p. 256°-258°). The sp.gr. referred to water is 
0-9292. The analysis agreed with the formula 
CjsHjj^ ; the vapour density could not be deter- 
mined, as it decomposes at 300°. The essential 
oil mixes in all proportions with alcohol, ether, 
or chloroform. 

The seeds themselves are used as food for 
birds, some kinds of -which are inordinately fond 
of them. They are roundish, ovate, of a grey 
colour, and contain 34 p.c. of oil and 16 p.c. of 
albuminoids. 

HEMP SEED OIL. Hemp seed is obtained 
from the seeds of the hemp plant, GanncAis 
sativa (Linn.). The hemp plant is cultivated 
in France, Belgium, Germany, Northern Italy, 
Algeria, Korth America, India, Manchuria, and 
Japan. A large quantity of the seed is still 
grown in France, where the oil is expressed for 
commercial purposes. The seeds yield about 
30 p.c. of oU. The colour of the freshly-ex- 
pressed oil is light-green to greenish-yellow, 
which becomes brownish-yeUow on keeping. 

Hemp seed oil contains a few p.c. of solid 
glycerides, most likely palmitin, with a small 
amount of stearin or arachin. The liquid fatty 
acids in hemp seed oil consist of linolio acid, 
and smaller quantities of oleic, and linolenic (and 
tsolinolenic (?)) acids. 

Hemp seed oil is used as a paint oil, though 
less frequently in this country than on the 
Continent. Considerable quantities are used on 
the Continent for making soft soap, characterised 
by a dark-green colour. The lower qualities of 
hemp seed oil are stated to be used in the 
manufacture of varnishes. J. L. 

HENBANE. Hyoscyamus. Jusquiame, Fr. ; 
Bilsenkraut, Ger. 

Henbane, Hyoscyamus niger (Linn.) (Bentl. 
a. Trim. 194), is one of the group of poisonous 
plants belonging to the natural order SolanacecB 
and is nearly related to belladonna, stramoni- 
um, andduboisia. It has been employed in medi- 
cine since the 7th century and an allied species, 
having similar properties, H. albus (Linn.) was 
known to Dioscorides. There are two varieties 
of B. niger, one an annual and the other a 
biennial. Both are to be obtained in the market. 



HENDECENOIC ACID 



39 



but the leaves or green tops of second-year plants 
of the biennial variety are the most active and 
should alone be employed in medicine. The 
seeds possess still greater activity, but they are 
only used in the manufacture of alkaloid. Hen- 
bane is a coarse hairy erect herb with pale-yellow 
flowers marked with purple veins, and the whole 
plant evolves an unpleasant odour. It occurs 
wild throughout Britain and most parts of 
Europe, Asia, and Northern Africa, and has been 
naturalised in North and South America. Hen- 
bane is employed as a sedative, anodyne, or 
hypnotic, and, like belladonna and stramonium, 
it dilates the pupil of the eye. Its activity is 
destroyed by the presence of free alkali, with 
which it should therefore not be administered 
(Garrod, Pharm. J. 17, 462 ; 18, 174). 

The active constituents of henbane are 
two isomeric alkaloids. The one, hyoscyamine 
CijHijNOj, was first obtained in a pure state by 
Geiger and Hesse (Annalen, 7, 270) and more 
completely studied by Hohn and Reichardt 
(Annalen, 157, 98) ; the other, present in much 
smaller proportion, hyoscine Ci,H25NOj, was 
discovered by Ladenburg (Annalen, 206, 282). 
Hyoscyamine also occurs together with atropine 
in belladonna and stramonium {v. Datitba), 
and ' duboisine,' the alkaloid of Duboisia 
myoporoides (B. Br.), is identical with hyoscine 
(Ladenburg and Petersen, Ber. 20, 1661). Both 
hyoscyamine and hyoscine, like atropine, are 
mydriatic alkaloids. 

To obtain hyoscyamine from henbane seeds 
Hohn and Beichardt first deprive them of fixed 
oil by treatment with ether and then exhaust by 
means of alcohol acidified with sulphuric acid. 
The clear extract, after removal of the alcohol 
by distillation, is almost neutralised by soda and 
precipitated with tannic acid. The moist preci- 
pitate is mixed with lime and extracted with 
alcohol. The alcoholic solution is acidified, con- 
centrated, and purified by washing with ether. 
The alkaloid is then set free by the addition of 
soda and isolated by extraction with ether. 
Other somewhat similar methods have been sug- 
gested by Bennard (Neues Bep. Pharm. 17, 91), 
Thorey (Pharm. J. [iii.] 12, 874), and Thibaut 
(Chem. Zentr. 1875, 665). Duquesnel (J. Pharm. 
Chim. [v.] 5, 131) extracts the seeds with hot 90 
p.c. alcohol containing tartaric acid, and from the 
solution obtained removes the alcohol by distilla- 
tion. There remains a residue of two layers, a 
lower syrupy and an upper oily layer, which latter 
is found to contain most of the tdkaloid, perhaps 
in combination with a fatty acid. This is 
extracted by treating the oil with water acidi- 
fied with sulphuric acid. The solution is 
nearly neutralised with potassium bicarbonate, 
concentrated to a syrup, and extracted with 
alcohol, which leaves potassium sulphate un- 
dissolved. The alcohol is removed from the 
solution by distillation, and the residue, diluted 
with water and treated with a slight excess of 
potassium bicarbonate, is extracted with chloro- 
form. The crude hyoscyamine is removed from 
the chloroform solution by water acidified 
with sulphuric acid, is purified by treatment 
with animal chaicoEtl', and the solution is then 
concentrated to a syrup. The alkaloid is set 
free by an excess of calcium carbonate, and 
mixed with sand, is dried over sulphuric acid. 
Finally, treatment with chloroform extracts the 



hyoscyamine and yields it on evaporation in large 
prismatic needles. 

Hyospyamine melts at 108-5° (Ladenburg) 
and dissolves more readily in water and dilute 
alcohol than atropine. It is Isevorotatory. By 
the action of barium hydroxide or hydrochloric 
acid hyoscyamine yields, in the same manner as 
atropine, tropins CjHijNO and tropic acid 
psHioP, (Ladenburg, Ber. 13, 254 and 607), but 
IS distinguished from that base by its metallic 
derivatives. Hyoscyamine aurichloride 

C„Hj,NO„HaAua, 
melts at 169°, whilst the isomeric atropine 
aurichloride melts at 137°. The appearance and 
solubility of the two salts are also different 
(Ladenburg). Hyoscine, which is obtained 
from the mother liquors after crystallisation of 
hyoscyamine, is a syrupy liquid. It. can, 
however, be obtained in crystals melEng at 
about 65° (Hesse, Annalen, 271, 100). The 
aurichloride melts at 198°. Hyoscine is idefitical 
with scopolamine, but the commercial scopola- 
mine is not obtained from this source (c/. 
Vboeto-alkaioids). 

Brandos, who analysed henbane seeds, found 
24 p.c. oi fixed oil (Berz. J. 21, 180) ; a substance 
' hyoscypicrin,' supposed to be a glucoside, was 
obtained by Hohn and Beichardt ; and the pre- 
sence of potassium nitrate in the leaves was 
pointed out by Thorey and in the medicinal 
extract by Attfield (Pharm. J. 3, 447). 

Hyoacyamua muiicus (Linn.), a species of hen- 
bane occurring in certain parts of India, and used 
in Indian medical practice, has been examined by 
Dunstan and Brown (Chem. SoC Trans. 75, 72), 
who find hyoscyamine to be the only alkaloid 
present in any notable quantity. A. S. 

HENDECATOIC or UNDECATOIC ACIDS 
OiiHjjOj. 

1. n-Undecylic acid CHj[CH2]8COOH is a 
crystalline solid having a faint smell of caproio 
acid ; it is obtained by the reduction of unde- 
oylenio acid or by the oxidation of methylunde- 
cylketone; m.p. 28-5°; b.p. 228° (160 mm.) 
(KrafEt, Ber. 1879, 1664). 

2. Methyl dibutyl acetic acid 

[C(CH3)3]2C(CH3)C00H 
is obtained with other products by the oxidation 
of jsotributyleue. A white crystalline solid, in- 
soluble in water, but soluble in alcohol or 
ether ; m.p. 66°-70° ; b.p. 260°. 

3. Vmbellviic acid OnHjjOa. The nuts of 
the Calif ornian bay tree {Umbellularia Calif or- 
m'co [Nutt.]) contain about 60 p.c. of a fat easily 
soluble in ether. It is a white, hard, tallowy mass 
m.p. 31°. By saponification with caustic potash 
and decomposition with hydrochloric acid, the 
acid is obtained as a white solid with a faint 
odour and very disagreeable and irritating taste ; 
m.p. 31°-34° ; b.p. 275°-280°. Its alkyl esters 
are colourless mobile liquids of agreeable odour 
(Spillman and O'Neill, Amer. Chem. J. 1882,206). 
Possibly identical with cocinic acid found by 
Saint-Evre in cocoa-nut oil, and with the 
undecylic acid of Krafft (v. supra). 

HENDECENOIC ACID CnHaoOj an acid boil- 
ing at 258°-261° found in petroleum ; known 
also as petroleumic acid. It is obtained from the 
petroleum distillate, b.p. 250°-270°, by adding 
sodium hydroxide and then to the alkaline ex- 
tract, sulphuric acid. This is treated with alcohol 



40 



HENDECENOIC ACID. 



and hydrochloric acid, and the resulting ester 
fractionated and hydrolysed with alcoholic 
potash (Hell and Medinger, Ber. 1874, 1217; 
1877, 451). 

HEPARADEN and HEPARON v. Synthetic 

DEUGS. 

HEPAR SICCi V. Synthetic drttqs. 
HEPATIC CINNABAR v. Cinnaeae. 
HEPTOIC ACIDS C,H,,Oj. 

1. n-Heptoic acid, oenarUhylic acid 

CH,(Cflj)5C00H. 
Obtained by the oxidation of oenanthol (Bussy, 
Annalen, 60, 248 ; Tilly, ibid. 67, 107 ; Krafit, 
Ber. 1882, 1717 ; Schorlemmer and Grimshaw, 
Annalen, 170, 141); also formed by the oxidation 
of castor-oil, of oleic acid, and of normal heptyl 
alcohol (Schorlemmer, Annalen, 161, 279 ; 
Tripier, Bull. Soo. chim. [iiL] 11, 99); from the 
normal hexyl cyanide (Franchimout, Annalen, 
165, 237); and by the redaction of dextrose- 
carboxylio acid (Kiliani, Ber. 1886, 1130). An 
oily liquid; b.p. 222-4'' (743-4 mm. ),m.p. -10-5', 
sp.gr. 0-9183, 20°/. 

2. isoSeploic acid ; a-methylhexoic acid 

CH,[CHj],CH(CH8)C00H. 
Obtained by boiling hexyl cyanide with alcoholic 
potash (Heeht, Annalen, 209, 309), or by the 
reduction of fructosecarboxylic acid (Klliani, 
Ber. 1885, 3071). An oUy rancid smelling liqpiid ; 
b.p. 211-5° (745-8 mm.), sp.gr. 0-9138, 21°/. 
Soluble in 278 parts water. 

3. Isooenanthylic acid found among the pro- 
ducts obtained by heating a mixture of socuum 
acetate and sodium tsovalerate ; b.p. 217°, sp.gr. 
0<9260, 15°/ (Portsch, Annalen, 218, 66). 

4:. isoAmyl acetic acid ; S-methylhexoic acid 
(CH,)jCH[CHj]3C00H. 
Obtained by the action of sodium and tVoamyl 
iodide upon ethyl acetate (Franldand and Duppa, 
Annalen, 138, 338), or by the distillation of iso- 
amylmalonic acid (Faal and Hoffmann, Ber. 
1890, 1498) ; b.p. 208°-210°, sp.gr. 0-9122, 13°/. 

6. Methyl diethyl acetic ac0 ; aa-methylethyl- 
butyric acid CH3(OjH5)jC-COOH. Obtained by 
prolonged heating of methyl diethyl carbinol 
cyanide with strong hydrochloric acid 
(Sohdanow, Annalen, 185, 120) ; b.p. 207°-208° 
(763 mm. ) ; almost insoluble in water. 

6. Methyl isopropyl propionic acid; fiy-di- 
melhylvaleric acid 

CH8(C3H,)OH-CHj-COOH. 
Obtained by heating sodium tsovalerate with 
sodium ethoxide in a stream of carbon monoxide 
(Loos, Annalen, 202, 321) ; b.p. 220°. 

7. Eihylpropylacetic acid; a-ethylvaleric acid 
CHs(CH,)jCH(CsiH5)C02H. Obtained by hydro- 
lysing ethylpropylacetoacetio ester with alkali 
(KUiani, Ber. 1886, 227) ; b.p. 209-2°. 

8. Active amylacetic acid; y-methylhexoic 
acid CH,(CsH5)OH-CHj-CH2-COOH. Obtained 
by heating active amylmalonic acid (Welt, Ann. 
Chim, Phys. [vii.] 6, 132) ; b.p. 221° ; sp.gr. 
0-9149, 20°/2'0^ 

9^ Mefhyliadbviylacetic acid ; ay-dimetJiyl- 
valeric acid. Obtained by heating methylido- 
butylmalonic acid (Burrows and Bentley, Chem. 
Soc. Trans. 1895, 611) ; b.p. 204°-206°. 

MO-HEPTYLAOETIG ACID v. Nonoio acids. 

»-HEPTYLSUCCINIC ACID 

C,Hi5-CH(C0jH)CH,-C0aH. 



Obtained by the reduction of hoxylita-, -citra- 
or -mesaconio acids with sodium amalgam 
(Fittig and Hoeffken, Annalen, 304, 337) j m.p. 
90°-91°. 

HERCULES METAL v. Ahiminium. 

HERCULES POWDER v. Explosives. 

HERMOPHENYL v. Synthetic DEtres. 

HERNIARINE v. Lactones. 

HEROIN V. Synthetic deuqs. 

HERRING OIL is obtained from the several 
species of herring, Clupea harengus (North Sea), 
G. PaUati, C. and F. (Japan). This oil is now 
extracted on a commercial scale in Japan, and 
genuine specimens of such oil have been 
prepared by Tsujimoto. The Japanese herring 
oil yields on brominating 3-82-6-5 p.c. of the 
octobromide of clupanodonic acid, which is a 
characteristic constituent of all fish oils. The 
herring oils produced in Europe (Norway) are 
not kept separate from other fish oils, , and, 
therefore, do not represent such pure oils as 
those described by Tsujimoto. The iodine value 
of genuine herring oil lies in the neighbourhood 
of 130, whilst the commercial North Sea herring 
oil exhibits higher iodine values. 

Like all other fish oils, herring oil is chiefly 
used in the leather industry. J. L. 

HESPERIDIN V. (Slucosides. 

HESSIAN PURPLE, RED, YELLOW, t>. 

AZO- COLOUKINO MATTEES. 

HETEROXANTHINE, 7-methylxanthine, 

NH-CO-C-NMe/ 
7-methyl-2 : 6-dioxypurine I It J^CH 

CO-NH-C— n/^ 
occurs together with xanthine and paraxanthine 
as a constituent of normal human urine (Salomon, 
Ber. 1885, 18, 3406; Virchow's Archiv. 1891, 
125, 564); 10,000 litres yielded 22-2 grams of the 
mixed bases, of which 11-36 grams was heteroxan • 
thine (Salomon and Kriiger, Zeitsch. physiol. 
Chem. 1898, 24, 364); it occurs also with 
xanthine in the urine of the dog (Salomon, ibid. 
1887, 11, 410). Heteroxanthine appears to be a 
product of the metabolism of theobromine and 
caffeine, for when rabbits, dogs, or men are 
dosed with these alkaloids, heteroxanthine 
appears in the urine (Bondzynski and Gottlieb, 
Ber. 1895, 28, 1113). According to Albanese 
(Gazz. cMm. ital. 1895, 26, ii. 298) heteroxan- 
thine is an intermediate product in the transfor- 
mation that caffeine undergoes in the- organism, 
the methyl' groups being removed one by one 
until xanthine is obtained, and this is converted 
into urea and ammonia. Heteroxanthine acts 
as a powerful diuretic on dogs and rabbits 
when hypodermically injected in small doses ; 
larger doses are toxic, an injection of 1 gram 
killed a dog weighing 8 kilos, in 10 days 
(Albanese, I.e.). (Cp. also Kriiger and Salomon, 
Zeitsch. physiol. Chem. 1895, 21, 169; 
Sohmiedeberg, Ber. 1901, 34, 2556.) 

The synthesis of heteroxanthine from 
theobromine has been effected by Fischer (Ber. 
1897, 30, 2400). When 2 : 6-dichloro-7-methyl- 

N : CCl-C-NMe. 
purine ( || >CH, obtained by the 

Ca : N-C — N^ 
action of phosphoryl chloride on theobromine, is 
heated at 120°-126° with hydrochloric acid 
(sp.gr. l-19),itisconverted into the hydrochloride 
of 7-methylxanthine or heteroxanthine. Kriiger 
and Salomon (Zeitsch. physiol. Chem. 1898, 28, 



HISTIDINE. 



41 



389) also obtained it by the action of nitrous 
acid on epiguanine, 7-methylguanine (2-amino- 

NH • CO • C-NMe, 
6-oxy-7-methylpurine) I l| \CH ; 



'1 Jl 

C(NH,):N-C — N< 
and as Fischer (2.c. ) has synthesised epiguanine, 
this method of piepaiation is also synthetical. 
Heteroxanthine is a crystalline powder; when 
heated gradually it melts and decomposes at 
341°-342°, when heated rapidly it darkens at 
360°, and melts and decomposes at 380°. It 
dissolTes in 142 parts of boiling water (Fischer, 
I.e.), or in 7575 parts of alcohol at 17°, or in 
2250 parts at the boiling temperature (Bondzyn- 
ski and Gottlieb, Ber. 1895, 28, 1113). Hetero- 
xanthine possesses both acidic and basic 
properties, the basic dissociation constant Ic^ 
being 3'754K; and the acidic dissociation 
constant fe„ being 1276K, where K is the dissocia- 
tion constant of water (Wood, Chem. Soc. Trans. 
1906, 1840). 

Heteroxanthine forms salts with acids that 
are readily dissociated in water, the hydrochloride 
crystallises in tufts of transparent crystals, and 
yields a microorystalline platinichloride ; the 
sulphate CjHjOaNj-HjSOi is decomposed by 
water. Heteroxanthine forms a characteristic 
sodium derivative NaC8HjOaN„5HjO, crystal- 
lising in plates or prisms, melting at about 300°, 
readily soluble in water, sparingly so in sodium 
hydroxide ; the potassium derivative has 
similar properties and a higher melting-point 
(Salomon, Ber. 1885, 18, 3406; Virchow's 
Archiv.- 1891, 125, 554). Heteroxanthine yields 
a crystalline precipitate with mercuric chloride, 
and forms a crystalline derivative with silver 
nitrate. It is also precipitated by copper 
acetate, phosphotungstic acid or lead acetate in 
the presence of ammonia (Salomon, I.e.). It is 
differentiated from hypoxanthine, xanthine, and 
guanine by the sparing solubility of its sodium 
derivative in sodium hydroxide ; it differs 
from paraxanthine in being amorphous and 
sparingly soluble, and in not yielding a precipi- 
tate with picric acid in the presence of hydro- 
chloric acid. 

When a solution of heteroxanthine containing 
chlorine water and nitric acid is evaporated, the 
residue develops a red colour with ammonia, 
becoming blue on the addition of sodium 
hydroxide. On oxidation with potassium per- 
manganate in concentrated sulphuric acid 
heteroxanthine yields three of its four nitrogen 
atoms as ammonia or carbamide, and the fourth 
as methylamine (Jolles, Ber. 1900, 33, 2126, 
2120). 

By electrolytic reduction in sulphuric acid 
solution, heteroxanthine yields 7-methyl-2-oxy- 
l : 6-dihydropurine (Tafel and Weinschenck, 
Ber. 1900, 33, 3374). M. A. W. 

HETOCRESOL, HETOFORM, HETOL 
CAFFEIN, HETRALIN v. Syuthetio deugs. 

HEXADECYtENEDICARBOXYLIC ACID, 
Tetradecylsuecinic acid CisHjjOj. Prepared by 
heating hexadecylenedibromide, potassium cya- 
nide, and alcohol at 160°-190°, and decomposing 
the nitrile thus formed with alcoholic potash 
(Krafft and Grosjean, Ber. 1890, 2355) ; m.p. 
121°. The anhydride melts at 89°. 

HEXAHYDROXYBENZENE v. Phenol and 

IIS HOHOLOGUES. 

c^cJo-HEXANONE v. Ketones. 



HEXOIC ACIDS V. Caproio aoids. 
HEXOSEPHOSFHORIC ACID v. Feembnta- 

TION. 

HEXOSES V. Cabbohydeates. 

HIDDENITE. A transparent, emerald-green 
variety of the mineral spodumene LiAISiaOe 
(q.v.), used as a gem-stone. It is found with 
emerald in North Carolina, and has been 
popularly, but erroneously, known as 'lithia- 
emerald.' L. J. S 

HIGHGATE RESINS v. Besins. 

HIN6 !). Gum ebsins. 

HIPPURIC ACID, Benzamino-acetie acid 
henzoylglycine NH(C,HjO)CHj-COaH, an acid 
found in the urine of horses and cows and 
other herbivora and in human urine when 
benzoic acid is taken internally. The crude 
acid obtained from urine is strongly coloured ; 
it may be purified by passing chlorine into the 
hot aqueous solution, filtering while hot, and 
rapidly cooling the filtrate. May be prepared 
by action of benzoic anhydride on glycocoU 
(Curtius, Ber. 1884, 1663). Crystallises in large 
trimetricprisms, soluble in water and alcohol; m.p. 
187-5°. Has a slightly bitter taste and reddens 
litmus. Decomposes on heating, forming ben- 
zonitrile and benzoic acid (Limpricht and Uslar, 
Annalen, 88, 133). Its aqueous solution boiled 
with mineral acids yields glycocoU (glycine) and 
benzoic acid. Oxidation with potassium perman- 
ganate in acid solution yields carbamide (Jolles, 
Ber. 1900, 2834). Hippuric acid may be detected 
in urine by treating a few c.c. with sodium 
hypobromite, just sufficient being taken to 
decompose the carbamide and impart a perma- 
nent yellow colour to the solution. If hippuric 
acid is present, a characteristic orange- or 
brownish-red precipitate is formed (Dehn, J. 
Amer. Chem, Soc. 1908, 1508). For quantitative 
estimation in urine v. Henriques and Sorensen 
(Chem. Zentr. 1909, ii. 2043; 1910, i. 870). 

HISTIDINE, glyoxaline-i-alanine, l-a-amino- 
fi-glyoxaline-i (or 5)-propionic acid, P-iminazole- 
a-aminopropionic acid 



NH— CH; 



I 3c-CHs-CH(NHj)C0jH 

CH=N 
was discovered by Albrecht and Kossel (Zeitsch.- 
physiol. Chem. 1896, 22, 176) among the hydro- 
lytio products of the protamine sturine, which 
contain 12'9 p.c. histidine, 12 p.c. lysine, and 
58-2 p.c. arginine (Kossel, ibid. 1900, 31, 207). 
Hedin (ibid. 1896, 22, 191) isolated it from the 
bases precipitated by silver nitrate from the 
decomposition products of other proteins. 
Kutscher {ibid. 1898, 26, 195) found it present in 
antipeptone obtained by the pancreatic digestion 
of fibrin. Lawfoff {ibid. 1899, 28, 388) and 
At)derhalden and Bona (ibid. 1904, 41, 278) pre- 
pared' it from thymus histon ; and Koch (J. 
Biol. Chem. 1911, 9, 121) established its presence 
among the hydroljrtio products of the globulin 
from pigs' thyroids. Histidine occurs also with 
arginine andlysineamongthehydrolytic products 
of vegetable proteins, notably in the seeds and 
seedlings of Picea excelsa (Link.), Pinua sylveatris 
(Linn.), Ciicubita Pepo (Linn.), Lupinua Iwteus 
(Linn,), and Pisvm sativum (Linn.) ; in the case of 
conifer seeds 300 grams of the dry proteid yield 3 
grams histidine hydrochloride, 19 grams arginine 
nitrate, and 3 grams lysine picrate (Schulze and 



42 



HISTIDINE. 



Wintefstein, Zeitsoh. physiol. Chem. 1899, 28, 
459; 465; 1901,33,547). 

The constitution of histidine as a-amino-$- 
glyoxaline-i (or 5)-propionic acid, has been estab- 
lished by the work of Frankel, Paiily, Knoopand 
Windaus, and Pyman. Frankel (Monatsh. 1903, 
24, 229) showed that histidine contains a carhoxyl 
group,since it displaces carbon dioxide from silver 
and copper carbonates, and an amino group 
becauseon treatment withhypobromiteor nitrous 
acid one nitrogen atom is removed and a hydroxyl 
group introduced. Frankel, therefore, represented 
histidine by the partially expanded formula 
NHj-CjHjNj-COjH, and gave the name histine 
to the complex — CjHjNj — , and hydroxyde- 
aminohistidine or hydroxyhistinecarboxylic acid to 
the compound OH-CjHsNa-COjH obtained from 
histidine by the action of nitrous acid. Pauly 
(Zeitsch. physiol. Chem. 1904, 42, 608) confirmed 
the presence of the carboxyl group in histidine 
by preparing the methyl ester, and proved that 
the histine complex — CjHjNj — contains an 
tmirao-group, because histidine yields a dinaphlha- 
lene-0-sulphone derivative, and forms a red dye 
with diazobenzenesulphonic chloride. These 
considerations, and the stability of the compound 
towards oxidising agents led Pauly to conclude 
that the complex histine contains an iminazole 
or glyoxaline ring, and that histidine is a-amino- 
P-glyoxaline-i (or 5)-propionic acid 

NH-CH^ 

I >C-CH8-CH(NHj)C0jH. 

ch=n/ 

This conclusion has been confirmed by Knoop. 
and Windaus (Beitr. Chem. Physiol. Path. 1905, 
7, 144), who obtained glyoxaline-4 (or 5)-j>ropionic 
acid 

NH-CH^ 

I >CCHj-CH,C08H 

CH=N-^ 

by reducing Frankel's hydroxydeaminohistidine, 
and showed that it is identical with the synthetic 
product prepared by the action of formaldehyde 
and ammonia on Wolff's glyoxylpropionic acid 
(Annalen, 1890, 260, 79). 

Knoop (Beitr. Chem. Physiol. Path. 1907, 

10, 111) also showed that by the successive 

oxidation of hydroxydeaminohistidine glyoxaline- 

NH-CH 



^\ 



dioxide and yields glyoxaline 



i(ai 5)-carioxylicacid I /C-COjH is db- 

ch=n/ 

tained, which, when heated at 286°, loses carbon 
NH-CH<. 

>GH. 
'CH=N^ 

The complete synthesis of iistidine from 4 
(or 5)-chloromethylglyoxaline is described by 
Pyman (Chem. Soo. Trans. 1911, 1386). 4 (or 5)- 
Chloromethylglyoxaline (I), obtained from dia- 
minoaoetone {ibid. 668), condenses with ethyl 
sodiochloromalonate to form ethyl 4 (or 5)- 
glyoxalinemethylchloromaUmate (II) 

NH'CiL 

>CCH,C1 



CH=N/ 



NHCH^ 

I ^CCHj-CClfCCOjEt), 



This ester on hydrolysis is converted into r-a- 
chloro-p-glyoxaline-i (or 5)-propiomc acid (III), 
which reacts with ammonia to form r-a-amino- 
0-glyoxaline-i (or B)-propionic acid (IV), that ia 
r-histidine 

NH-CH. 

1 \cCHsi-OHaCOjH 

ch=n/ 

III. 



NH-c: 



^C-CHj-CH(NHj)COjH 
IV. 



r-Histidine can be resolved by the fractional 
crystallisation of the salts it forms with f2-tartaric 
acid into the d- and /- isomerides, and the 2- 
histidine thus obtained is identical with the 
naturally occurring compound. 

A possible explanation of the formation of 
histidine in the plant economy is afforded by the 
work of Knoop and Windaus (Beitr. Chem. 
Physiol. Path. 1905, 6, 392; Ber. 1906, 39, 
3886 ; 1907, 40, 799) on the synthetic formation 
of iminazole derivatives from sugars and 
ammonia. Thege authors find that when a 
solution of glucose containing zinc hydroxide 
dissolved in ammonia is exposed to the sunlight 
at the ordinary temperature for some weeks, it is 
converted to the extent of 10 p.c. into 4- or 
5-methyliminazole. It is probable that glyoxal 
and formaldehyde are produced as intermediate 
products and then react with the ammonia 
according to the equation 
MeCO H,N Hv MeC-NHx 



O^ CI 



^, 



./' 



CH+3HjO 



ch=n/ 



II. 



COH HjN O^ CH-N^ 

(f-Mannose, d-fructose, d-sorbose, i-arabinose, 
or Z-xylose also yield methyliminazole when 
similarly treated. The authors suggest that 
histidine may be formed naturally by the 
condensation of methyliminazole with glycocoll 
and simultaneous oxidation 
NH-CH^ 

I >C-CH,+CHa(NH,)COjH+0 

CH=N^ 

NH-CH^ 
= 1 >C-CH2-CH(NH2)COi,H+HiiO. 

Histidine crystallises from water in needles 
or tables, m.p. 287° (corr.) ; the aqueous solution 
has a sweet taste (Frankel, Monatsh. 1903, 24, 
229 ; Pyman, Chem. Soc. Trans. 1911, 1397), is 
feebly alkaline (Hedin, Zeitsch. physiol. Chem. 
1896," 22, 191 ), and is optically active [olj,— 39-74° 
(Kosse! and Kutscher, ibid. 28, 382) ; [a]„-36-7° 

(Pyman, I.e.). 

r-Histidine crystallises in quadrilateral plates, 
and decomposes at 283° (corr.) ; d-histidine 
crystallises in monoolinio plates forming elon- 
gated hexagons; it decomposes at 287-288° 
(corr.). and has [a]j,+ 39-3° (Pyman, I.e.). 

When histidine is administered as a food, oi 
by intravenous injection very little (0-4 gram out 
of 10 grams) is recoverable as such in the 
urine ; the urea and ammonia in the urine are 
largely increased, but the increase of allantoin 
is very slight (Abderhalden, Einbeok and 
Sohmid, Zeitsoh. physiol. Chem. 1909, 62, 322 ; 
1910, 68, 395 ; Kowalewsky, Bioohem. Zeitsch. 
1909, 23, 1). 



HISTIDINE. 



43 



Salts. 2-Histidine forms stable salts with 
acids and their solutions are dextrorotatory. 

Momhydrochhride GjH.OaNa-HCl.HjO forms 
large colourless rhombic crystals 

o:5:c=0-7665: 1:1-71104, 
has [o]d + 1-74°, m.p. 80°, and loses HjO at 
140° (Albreeht and Kossel, Zeitsch. physiol. 
Chem. 1896, 22, 176 ; Hedin, ibid. 191 ; Kossel 
and Kutsoher, ibid. 1899, 28, 382; Frankel, 
Monatsh. 1903, 24, 229) ; the di-hydrochloride 
C,H,0aN,-2HCl is isomorphous trith the mono- 
compound [a : 6 : c=0-76537 : 1 : 1-77516], it has 
[o]d+5-3° to 6-4° (Kossel and Kutsoher, I.e. ; 
Schwartze, Zeitsohg physiol. Chem. 1900, 29, 
493). Histidine cadmium chloride 
C.HaOjN.-HaCdCl, 
melts and decomposes at 270°-275° (Sohenck, 
ibid. 1904, 43, 72). Histidine monopicrolonate 
CuHjOjNa-CioHsOjNj is yellow. The dipicro- 
lonate 0,5,0, 'N^-2Gi„B.gO^^, is orange (Steudel, 
Zeitsch. physiol. Chem. 1905, 44, 157; Brig], 
ibid. 1910, 64, 337) ; the dipicrate 
Ci»H,50„N„2H,0 
has m.p. 86° (corr.), (Pyman, Trans. Chem. Soo. 
1911 343). 

l-Bistidine-d-hydrogen tartrate 
C,H,0aN3.C4H,0, 
is easily soluble in water, crystallises in large 
well-defined prisms, and decomposes at 172°-173° 
(corr.); andha3[a]jj+16-3°. l-Hisfidine-l-hydro- 
gen tartrate is sparingly soluble in cold water, 
crystallises in clusters of prisms and decomposes 
at 234° (corr.), and has [alj,— 12-1° (Pyman, ibid. 
1397,1400). 

d-Histidine-d-hydrogen tartrate is sparingly 
soluble, decomposes at 234° (corr.), and has 
[a]j,-f 13-3° (Pyman, I.e.). 

r-Eistidine mono-hydrocMoride 
C,H,0,N,-Ha,2HjO 
has m.p. 117°-il9° (corr.); seaquihydrochloride 

(CeH,02N3)j-3HCl,H,0 
has m.p. 168°-170° (corr.); the dihydrochloride 
has m.p. 235°-236° (corr) ; r-histiiine mond- 
picratc C, jHi,0(,N5,H:jO decomposes at 180°-181'' 
(corr.) ; the dipicrate Ci8HibOi8N9,2H20 decom- 
poses at 190° (corr.), (Pyman, ibid, 339). 

Derivatives. Histidine methyl ester hydro- 
chloride CjH'8Ni,-COjMe-2HCl forms flat rhombic 
prisms, m.p. 196° (decomp.), the free ester is an 
oil (Pauly, Zeitsch. physiol. Chem, 1904, 42, 
608). Chhrohistinecarboxylic acid {a-chloro-p- 
glyoxaline- 4 (or 5)-propionic acid) forms thick 
prisms, m.p. 191° (decomp.), the corresponding 
ractmic compound decomposes at 201° (corr.) 
(Pyman, ibid. 1394), the oxalate of the ester has 
m.p. 161° (Windaus and Vogt, Beitr. chem. 
Physiol. Patli. 1908, 11, 406). Histidine 
anhydride CiaHiiOjNj forms glittering prisms, 
m.p. 340° (!Fwcher and Suzuki, Sitzungsber. K. 
Akad. Wiss. Berlin, 1904, 1333) ; the Z-anhydride 
has m.p. 328° in a closed evacuated tube, 
crystallises with 2iHaO, and has [a]!""— 66-24° 
in normal hydrochloric acid solution ; the 
dl-anhydride also has m.p. 328°, and is obtained 
by heating the ethyl ester of histidine at 160° 
(Pauly. Zeitsch. physiol. Chem. 1910, 64, 75) ; 
the pjsrate . decomposes at 255° (corr.); the 
hydrochloride at 320°. The tetraiodo derivative 
has m.p. 240°, and is amphoteric and forms a 
silver salt (Pauly, Ber. 1910, 43, 2243). 



^c-cHj-ch:(nh2)C0sH ; 



Histidylhistidine CuHuOjNj forms a yellow 
picrate, m.p. I66°-175° (Fischer and Suzuki, Z.e.). 
Of the acyl derivatives of histidine the benzoyl 
has m.p. 249° (decomp.) (Pauly, I.e. ; Frankel, 
l.B.) • the dinaphthnlene fi-sulphone 
C,H,0aN3(S0,-C,„H,), 
melts at 149°-lfi0° (Pauly); p-Nitrobenzoyl 
CjHsNjOj-COCeH^-NOs m.p.261°-252° (Pauly). 
Bemoyldiiodohistidine, m.p. 161°-164°, in an 
evacuated tube ; and p-nitrobenzoyldiiodohisti- 
dine, m.p. 172° (decomp.) are derivatives of the 
unknown diiodohistidine 

NH:1C5>^ 

I ^r 

CI:NH^ 

they give orange-red colourations with diazo- 
benzenesulphonic acid and sodium carbonate, and 
form silver salts (Pauly, Ber. 1910, 43, 2243). 
d-a-Bromoisohexoyl-l-Mstidine methyl ester 

CjHs-CHBr-C0-NH-CH(C4HjNj)C0aMe 
has ih.p. 176° (corr.); d-a-bromoisohexoyl-l- 
AiXWine CijHijOaNjBr has m.p. 118° (corr.); 
l-leiicyl-l-histidine 

C4H9-OH(NH2)-CO-NH-CH(C4H5NJCOjH 
crystallises in plates or prisms, containing HjO, 
which it loses at 100°/15-20 mm., and has 
m.p. 178° (corr.) (decomp.), the copper salt forms 
deep violet crystals ; formyl-l-histidine has m.p. 
203° (corr.) (Fischer and Cone, Annalen, 1908, 
363, 107). 

Colour reactions. Histidine gives the biuret 
reaction (Herzog, Zeitsch. physiol. Chem. 1903, 
37, 243). It also gives the Weidel pyrimidine 
reaction .under the following conditions: a 
solution of histidine hydrochloride and a little 
potassium chlorate is evaporated to dryness, 
hydrochloric acid containing one drop of nitric 
acid added and the solution again evaporated ; 
on exposing the residue to ammom'a fumes an 
intense red colour is produced, becoming 
reddish- violet on the addition Of sodium hydrox- 
ide (Frankel, I.e.). With diazobenzenesulphonic 
chloride in the presence of sodium carbonate 
histidine gives a dark cherry-red colouration, 
becoming orange on the addition of an acid. 
This is an extremely delicate test for histidine, 
and with the exception of tyrosine no other 
product of protein hydrolysis gives a similar 
reaction (Pauly, Zeitsch. physiol. Chem. 1904, 
42, 608). Histidine develops a yellow colour 
with bromine water; this disappears on warming, 
but after a time a pink colour appears, which 
afterwards deepens to a wine red. The reaction 
is sensitive with solutions of 1 : 1000, but is 
destroyed by too large excess of bromine water 
(Knoop, Beitr. Chem. Physiol. Path. 1908, 11, 356). 

Decomposition. When histidine undergoes 
anaerobic bacterial cleavage by the action of putre- 
fying pancreas, it is converted almost quantita- 
tively by the loss of carbon dioxide into 4 (or 6)- 
$-aminoelkylglyoxaline (B-iminazolylethylamine) 
NH-CH^ 



^\ 



CH:ir^ 

NH-CH. 
acid 



C-CHj-CHj-NHj ; iminazolylpropionic 



\ 



C-CHj-CHa-COjH being the other 



CH:N^' 

product. The 4 (or 5)-;8-aminoethylglyoxaline 
thus obtained is identical with the base prepared 
synthetically by Windaus and Vogt (Ber. 1907, 
40, 3691) from ethyl iminazolylpropionate ; or 



44 



HISTIDINE. 



4)y Pyman (Chem. Soo. Trans. 1911, 668) from 
diaminoEusetone, and is also identical with 
one of the ergot bases isolated by Barger and 
Dale (Phil. Trans. 1910, 2592), and which is also 
present in Popielski's vaso-dilaiin (Barger and 
Dale, J. Physiol. 1911, 41, 499). It has a direct 
stimulating action on plain muscle; cardiac 
muscle is mildly stimulated, and skeletal muscle 
is not affected. The drug produces narcosis, 
and is a mild stimulant to the salivary glands and 
pancreas. M. A. W. 

HOANG-NAN v. Nirx vomica. 

HOFMANN'S VIOLET v. Tmphenyl me- 
thane COLOUBmO MATTBB3. 

HOG GUMb. Gtos. 

HOLLANDITE. A manganese ore of essen- 
tially the same composition as psilomelane, but 
occurring in a crystallised condition, usually as 
fibrous masses and sometimes as cr^^stals. It is 
a manganate with the general formula 
m^Ra"^MIiOf+nR^"'(MnOs)^, 
where R" is Mn, Ba, Kj, Hj, (Fe, Ca, Mg, Na, 
Co, Ni, Cu), and R'" is Mn, Pe, (Al). It coiitains 
about 70-75 p.c. of manganese dioxide. The 
colour is greyish-black, and the lustre sub- 
metallic ; sp.gr. 4-70-4-95; H. 4-6. The 
mineral occurs abundantly in the manganese ore 
deposits at several places in Central India, and 
is largely exported from the mines at Sitap^r 
and B414gh4t. (L. L. Fermor, The Manganese 
Ore Deposits of India, Mem. Geol. Survey India, 
38.) L. J. S. 

HOLOCAINE V. Synthetic DEiras. 

HOMBERG'S PHOSPHORUS v. Caloittm. 

HOMOANTHRANILIC ACID v. Amino acids 
(akomatic). 

HOMOCATECHOL v. EomopyrocatecM, 
Phenol and its HOMOLoauES. 

HOMOGENTISIC ACID v. Phbnylacbtio 
. acid. 

HOMORENON v. Syuthbtio drugs. 



HOMOTERPENYLIC ACID v. LactokeS. 

HONEY. Honey is the substance secreted 
by the working-bee {Apis mellifica) from the 
nectar of flowers, and deposited by the insect in 
the wax-cells forming the honeycomb. Its es- 
sential constituents are varying quantities of the 
sugars, dextrose, Isevulose, and sometimes cane- 
sugar, together with a small quantity of water. 
It also contains very small quantities of wax, 
colouring matters, aromatic substances, phos- 
phoric acid, nitrogenous compounds, and occa- 
sionally mannitol. 

The relative proportions in which the three 
above-named sugars occur is very variable. 
Thus Hehner (Analyst, 9, 164) obtained the 
following results from the analysis of 25 different 
varieties : 

MATJTmlTn MinlTnliTiq Mean 

Water . . 23-26 12-43 19-3 

Glucose . . 75-34 61-42 67-2 
Other constituents 16-51 8-48 13-6 

In 8 cases the amount of glucose was un- 
altered by inversion, in 7 increased, and in the 
remainder slightly diminished. 

Sieben (Bied. Zentr. 1885, 134) analysed 
60 specimens of honey, and states that the 
quantity of cane-sugar may amount to as much 
as 4 or even 8 p.c, and that the ratio of dextrose 
to Isevulose varies considerably, the total amount 
of these two sugars being 68-78 p.c. The average 
composition of the 60 specimens was as follows : — 
Dextrose . . . 34-71 p.c. 
lisevnlose . . . 39-24 „ 
' Sucrose . . . 1-08 „ 

Water . . . 19-98 „ 

Non-saccharine matter . 5-02 „ 
Turning now from average results to the 
composition of the several varieties, we find the 
following table of the analysis of 9 specimens 
of honey from different localities (J. C. Brown, 
Analyst, 1878, 257). 



— 


England 


Wales 


Nor- 
mandy 


Ger- 
many 


Greece 


Lisbon 


Jamaica 


Cali- 
fornia 


Mexico 


Water expelled at 100° . 


19-10 


16-40 


15-50 


19-11 


19-80 


18-80 


19-46 


17-90 


18-47 


Water expelled at a high 




















temperature and loss 


7-60 


6-56 


4-95 


11-00 


7-80 


6-66 


7-68 


8-13 


10-03 


Laevulose . 


36-60 


37-20 


36-88 


33-14 


40-00 


37-26 


33-19 


37-85 


35-90 


Dextrose 


36-55 


39-70 


42-50 


36-58 


32-20 


34-94 


35-21 


36-01 


35-47 


Sucrose 


1 


— 


— 


— 


— 


1-20 


2-20 


— 


? 


Wax, pollen, and in- 




















soluble matter . 


trace 


trace 


trace 


trace 


0-05 


1-00 


2-10 


trace 


trace 


Mineral matter . 


0-15 


0-14 


0-17. 


0-17 


0-15 


0-14 


0-26 


0-11 


0-07 



The characteristic composition of ordinary 
honey can be judged from the analysis of 10 
samples of genuine honey by Eoitsema (Zeitsoh. 
anal. Chem. 1899, 439) which gave the following 
results : — 



Specific gravity . 

Water 

Rotation , 

Ash 

Pollen and wax . 

Reducing sugars 

Sucrose 



1-102-1-140 
8-3-17-8 p.o. 
-9-1° to -30° 

0-12-0-34 p.c. 

002-0-46 „ 

71-2-74-4 „ 
0-2-6-4 „ 



The amount of water present in honey varies 
with the dryness of the season and the conditions 
of storage, evaporation being much lessened 



when all the cells of the comb are closed (Graftian, 
Analyst, 1895, 251). 

Brlenmeyer and v. Plata (Rep. Pharm. 23, 610) 
found that in 6 samples of good honey the amount 
of water varied from 17-5 to 19-5 p.c, whilst a 
liquid honey from Senegal contained as much 
as 25-6 p.o. The amount of phosphoric acid 
present (calculated on the dfied substance) 
varied from 00123 to 0-883 p.c. , 

_ Sumatra honey, formed by Apia indica, con- 
tains water, dextrose, Isevulose, a little wax and 
pollen, and 0-23 p.c. ash, but no cane-sugar or 
dextrin (Franohimont, Rec trav. chim. 1, 223)-. 
An Ethiopian honey, made in hollows without 
wax by a kind of mosquito, gave the following 
result on analysis (Compt. rend. 88, 292) : 



HONEY. 



45- 



Water .... 


25-5 


LsBTulose and dextrose (|) 


320 


Mannitol 


30 


Dextrin .... 


27-9 


Ash ... . 


2-5 


Other constituents . 


91 



It has also been shown (Vogel, Ber. IS, 2271) 
that all honey contains a small quantity of 
formio acid, derived from the stings of the bees, 
and that to this is due the fact that honey keeps 
so well. It amounts only to 0-0011-0-0024p.c., 
therefore most of the acidity of honey must be 
due to some other acid, possibly malic acid (Parn- 
^ateiner, Zeitsch. Nahr. Gennssm. 1908, 16, 698). 

The formio acid may be estimated by con- 
version into sodium formate, heating with cono. 
sulphuric acid, and measuring the volume of 
carbon monoxide evolved. As lactic acid also 
gives this gas it must be oxidised with potassium 
permanganate and estimated as oxalate and a 
correction applied (Merl, Zeitsch. Nahr. Genussm. 
1908, 16, 385). 

If bees be fed on dextrose only, the honey 
formed contains that sugar alone. Heather-fed 
honey, on the other hand, contains invert sugar 
only, whilst Cuban honey contains dextrose in 
larger quantity than leevulose (Boders, Chem. 
Zentr. 1864, 1002). 

Eucalyptus honey is produced in Australia 
by a black bee which buUds large hives on the 
Eucidyipii containing as much as 5000 kilogs. of 
honey. The honey is a thick syrup, having a 
strong aromatic odour (Maquenne, Ann. Chim. 
Phys. [vi.] 17, 495). 

Marck has given the following figures for 
the composition of East Indian honeys (Analyst, 
1890, 196) :— 

Glucose, about 30 p.o. ; laevulose, 23-37 p.c. ; 
ash, 0-12-0.64 p.c. ; sp.gr. 1-3P99-1-3586; 
rotation +13° to -2° 64'. 

In the honey of Polyhia apicipennis large 
crystals of cane-sugar are frequently found 
(J. pr. Chem. [i.] 71, 314). The honey of the 
Mexican honey-ant is almost a pure solution of 
IsBVuIose, *nd when dried in vacu6, has the 
oompositiou CeHjjOj.H^O. It contains traces 
of a volatile acid which reduces silver salts 
(J. pr. Chem. [i.] 58, 430). 

To obtain honey the syrup is first simply 
allowed to flow from the comb at the ordinary 
temperature, the portion thus collected being 
known as ' virgin-honey.' As soon as the flow 
ceases, the residual comb is heated and pressed, 
t)y which means a darker and less pure variety 
is obtained. According to Zwilling (Bied. Zentr. 
1885, 67) it is best to gather the honey when 
it has thickened and the cells are sealed; as then 
sufficient sugar and formic acid are present. 

The honey-syrup remains clear for a long 
time if kept in the dark, but on exposure to 
light dextrose gradually separates, and %uch 
varieties as contain that sugar in the largest 
quantity become sufficiently solid to be cut with 
a knife into pieces which are not hygroscopic. 
As, however, the composition of honey is so 
variable, the consistency and colour likewise 
differ considerably in the different samples. 
Thus Narbonne honey has a light yellow colour, 
and forms an almost solid mass, whereas Cuban 
honey is a clear and almost colourless syrup. 

Honey has a sp.gr. of from 1-439 to 1-448. 



When diluted with water it gives a somewhat 
cloudy, faintly add solution, the cloudiness being 
due to small quantities of proteid matter. Its 
speciflo rotatory power varies from —1-5 to -f 2, 
but dextrorotatory honey is exceptional. 

Friihling has shown (Zeitsch. offentl. Chem. 
4, 410) that freshly prepared solutions of honey 
in cold water show an abnormal rotation, 
which, after some hours, becomes normal. This 
behaviour, which is due to ' bi-rotation,' may 
lead to erroneous observations unless care is 
taken to dissolve the honey in boiling water 
and to add about 0-1 p.c. of ammonia. 

A pure solution of honey does not readily 
undergo alteration in the air, but when impure, 
both acid and alcoholic fermentation speedily 
take place. An alcoholic liquor known as 
' mead ' (Ger. Mdh ; Pr. Hydromel) has long 
been prepared from honey by fermentation. The 
process is, however, frequently unsuccessful, 
owing to the fact that honey does not usually 
contain sufficient nitrogenous food for the sus- 
tenance of the ferment. If a suitable food be 
added, the fermentation proceeds smoothly 
and with certainty (Gastine, Compt. rend. 109, 
479). According to Boussingault (Ann. Chim. 
Phys. [iv.] 26, 362) the quantity of carbon 
dioxide formed during fermentation is greater, 
and the quantity of alcohol less, than would be 
expected from the amount of sugar fermented. 
Thus, instead of the calculated quantities of- 
193-6 parts of alcohol and 170 parts of carbon 
dioxide, he obtained 177-6 parts of alcohol, and 
190 parts of carbon dioxide. 

For medicinal purposes honey is purified by 
warming on the water-bath, and straining it 
through flannel which has been previously 
moistened with hot water. The purified com- 
pound is known as Md depuratum. Dietrich 
(Chem. Zentr. 1877, 318) brought a filtered 
solution of 1 part of honey in 3 parts of watei 
on to a dialyser, and found that 50 p.c. of the 
honey passed through. The solution of the 
crystalloids gave on evaporation a honey having 
an unusually pleasant aromatic taste. The 
colloidal liquid, in which gummy flocoulss 
remained suspended, gave on evaporation a 
syrup possessing a. purely sweet, insipid, non- 
aromatic taste. 

In order to purify honey Biecker (J. 1873, 
1066) adds a little precipitated aluminium hy- 
droxide, which carries down any fbreign sub- 
stances present. If ordinary honey be shaken 
with absolute alcohol, dextrose remains behind. 
Ether precipitates Issvulose from the alcoholic 
solution, and the ethereal solution when shaken 
with lime loses tannic acid, whilst wax remains 
in solution. 

Honey is frequently adulterated with starch- 
sugar, invert-sugar, molasses, water, &o., and 
owing to the wide variations in the composition 
of genuine honey such adulteration is frequently 
difficult to detect (Bacine, Zeitsch. offentl. 
Chem. 1902, 28l). 

Dextrorotatory honey was formerly regarded 
with suspicion (Haenle, Zeitsch. anal. Chem. 

1894, 99), but it has been shown that pine-honey, 
and lioney made by bees using honey-dew, 
contain a dextrin which can be isolated by pre- 
cipitation with alcohol; and is strongly dextro- 
rotatory (Konig and Karsch, Zeitsch. anal. Chem. 

1895, 1; Baumer, ibid. 1896, 397; Hilger, 



46 



HONEY. 



Zeitsoh. Nahr. Genussm. 1904, 189). For a, 
detailed account of the 'honey-dextrins'of pine- 
honey, see Haenle and Scholz (Zeitsch. Nahr. 
Genussm. 1903, 1027). 

Several methods have been recommended 
for distinguishing between genuine and adulte- 
rated honey. Brautigam states that genuine 
honey contains an albumin by the reactions of 
which it can be distinguished (Pharm. Zeit. 47, 
109). Methods for the microscopic examination 
of Tioney have been described by Dietrich 
(Analyst, 1896, 255). Langer has found in 
natural honey an inverting ferment which can 
be precipitated by alcohol and tested on cane- 
sugar (Zeitsch. angew. Chem. 1902, 1041). 

Adulteration with starch-syrup, which usually 
contains erythro-dextrin and amylo-dextrin 
can usually be detected by adding methyl 
alcohol to the cone, aqueous solution, when the 
dextrins are precipitated. The addition of 
molasses is best detected by testing for rafSnose 
with basic lead acetate (Beokmaun, Zeitsch. 
anal. Chem. 1896, 263). 

Ley's reagent, an ammoniacal solution of 
silver oxide, when warmed with a strong solution 
of pure honey gives a greenish colouration, but 
if the honey is adulterated the liquid becomes 
dark-brown or black (Utz, Zeitsoh. angew. Chem. 
1907, 993). 

If 1 gram of honey be rubbed down with 
ether in a mortar, the ether filtered ofi and 
evaporated, and the residue tfeated with a drop 
of a solution of 1 gram resorcinol in 100 c.c. of 
hydrochloric acid of sp.gr. 1-19, only a momen- 
tary pink colour will be obtained with pure 
honey, whilst adulterated or artificial honey wiU 
give an orange-red colour changing through 
cherry-red to a strong brown-red (Rehe, Zeitsoh. 
Nahr. Genussm. 1908^ 76; Keiser, Analyst, 
1909, 399). 

Adulteration with cane-sugar may be de- 
tected by determining the reducing power of 
the honey for Fehling's solution, both before 
and after inversion. This, however, is not very 
reliable, as in cases where the bees feed on 
sucrose considerable quantities are found in the 
honey, though the larger proportion undergoes 
inversion in the insect's stomach (Baumer, 
Zeitsch. anal. Chem. 1902, 333 ; see also Lipmann 
Analyst, 1889, 20). 

Sugar in honey is estimated by diluting with 
twice its volume of water, and ascertaining the 
sp.gr. This varies between l-lOl and 1-115. 
The first number corresponds to 24 p.c, and the 
latter to 27 p.c. of sugar in the solutions, or to 
72 p.c. and 82 p.c. in the original honey (Fliicki- 
ger, Pharmaceut. Chemie, [ii.] 267). 

Wiley has described a process for the estima- 
tion of Isevulose jn honey, &c., based on the 
fact that its optical rotation is much diminished 
with rise of temperature. The observation tube 
of the polarimeter is jacketed, and can be 
cooled to zero or heated to 88° at which tempera- 
ture a mixture of molecular proportions of 
dextrose and Isevulose becomes optically inactive 
(J. Amer. Chem. Soc. 1896, 81). 

HONTHIN V. Synthetic DBtros. 

HOPEiiNE is a crystalline alkaloid said to bo 
contained in wild American hops. It melts 
below 100° and partially sublimes below 160°. 
It is doubtful, however, whether it really exists 
(Ladenburg, Ber. 1886, 19, 783; J. Pharm. 



Chim. [v.] 12, 460; Williamson, Chem. Zeit. 
1886, 10, 20, 38, 207, 238, 491). 

HOPS V. BBBWDfO. 

HORDEIC ACID v. Dodecatoio acid. 

HORDEIN V. Barley, art. Bkewinq. 

HORDENINE {p-Hydroxyphehykthyldimethyl- 
amine) CioHjjNO was discovered by Le'ger 
(Compt. rend. 1906, 142, 108) in malt culms 
from which it is extracted by Stas' method. 
The ethereal solution of the alkaloid thus ob- 
tained is evaporated to dryness and the horde- 
nine residue is purified by repeated recrystallisa- 
tion from alcohol. Its constitution wag deter- 
mined by Leger (Compt. rend. 1906, 143, 234, 
916) and by Gaebel (Arch. Pharm. 1906, 244, 
435). 

Hordenine has also been synthesised from 
phenyl ethyl alcohol (Barger, Chem. Soc. Trans. 
1909, 2194 1 Le'ger, Bull. Soc. chim. 1910, [iv.] 
7, 172), and by the methylation of ;8-ji-methoxy- 
phenylethylamine hydrochloride with alcohoUc 
potash and methyl iodide at 100° (Bosenmund, 
Ber. 1910, 43, 306). 

Properties. — ^Hordenine forms colourless, al- 
most tasteless anhydrous orthorhombic prisms, 
m.p. 117-8° and subliming like camphor at 140°- 
150°. It is readily soluble in alcohol, ether, or 
chloroform, but sparingly so in benzene, xylene, or 
toluene. It is a strong base, is alkaline towards 
litmus and phenolphthalein, liberates ammonia 
from its salts, reduces acid solutions of potassium 
permanganate in the cold and ammoniacal solu- 
tions of silver nitrate and iodic acid on warming. 
It is not attacked by concentrated sulphuric acid 
OE by potash, but readily forms soluble salts 
with acids. When boiled with nitric acid it 
yields picric acid, and when methylated and 
oxidised with alkaline permanganate it gives 
anisic acid (Leger, J. Pharm. Chim. 1907, 26, 
6 ; Compt. rend. 1907, 144, 488). 

Hordenine sulphate crystallises in needles and 
has a slightly bitter taste. It forms brown 
crystals with iodine, but gives no precipitate 
with the tannins of vegetable infusions. In 
small doses it has a tonic action on the heart, 
but in toxic doses (1-2 grams per kilo) it pro- 
duces the reverse eSect. 

It has been employed as a remedy in cases of 
typhoid, dysentery, enteritis, &o. It is not so 
energetic as digitalis, sparteine, or strophanthus, 
but is less toxic than any of these (Sabraz^s and 
Guereve, Compt. rend. 1908, 147, 1076 ; see also 
Camus, ibid. 1906, 142, 110, 237). 

Hordenine methiodide, which probably 
possesses a similar physiological action to that 
of adrenaline, has been synthesised from p- 
methoxyphenylethylamine by treatment with 
methyl iodide,' an almost quantitative yield 
being obtained. It crystallises in colourless 
prisms, m.p. 229°-230° (Bosenmund, I.e.). 
Ot^er organic and inorganic compounds of 
hordenine have also been obtained (Leger, l.c., 
and Compt. rend. 1907, 144, 208). 

Detection. — ^A few drops of hordenine are 
dissolved in a few c.c. of acetic acid and boiled 
with a few drops of formaldehyde; 3 c.c. of 
sulphuric acid is now added when a green 
colouration is produced (Deniges, BuU. Soc. 
chim. 1908, [iv.] 3, 786). 

1 c.c. of 1 p.c. hordenine sulphate solution is 
boiled with an equal volume of urotropine solu- 
tion of the same strength, and 2 c.c. of strong 



HORSE-CHESTNUT. 



47 



sulphuric acid, a fine emerald green coloui is 
produced even with 0-0001 gram of hordenine 
sulphate (Labat, J. Fharm. Chim: 1909, 29, 
433). 

HOREHODND v. Mabbubium. 

HORN LEAD v. Lead. 

HORN QUICKSILVER. Calomel v. Mebouby. 

HORNSILVER. Native silver chloride v. 
Cbkakqykite, Silver. 

HORSE-CHESTNUT. Eippocastanum. Mar- 
ronier d'Inde, Fr. ; Rosscaatanien, Ger. The 
well-known horse-chestnut tree, Aculus hippo- 
casianum (Linn.), is a native of Persia and 
Northern India. It wag introduced into Europe 
in the 16th century, and is now largely cultivated 
for ornament throughout the temperate regions 
of the world. It is unimportant in medicine ; 
but it is interesting chemically as the source of 
several glucosides and allied compounds. 

Besides tannin (Bochleder, Zeitsch. Chem. 
1867, 76), fat, and constituents common to 
plants, horse-chestnut bark contains the gluco- 
side sesculin CisHjjOs (Minor, Berz. J., 12, 274 ; 
Jonas, Annalen, 16, 266) and in smaller propor- 
tion aseuleiin CsHjOj (Rochleder, J. 1863, 
589) which is also a product of the action of 
dilute acids or emulsin on Ksculin (Rochleder 
and Schwartz, Annalen, 88, 356). Fraxin or 
paviin OijHuO,,, a gluooside occurring in the 
bark of the common ash, Fraxinus excelsior 
(Linn.), is another constituent of horse-chestnut 
bark (Stokes, Chem. Soc. Trans. 11, 17; 12, 126) 
accompanied by fraxetin CjoHgOj (Rochleder, 
Chem. Zentr. 1864, 415), also produced when 
fraxin is boiled with dilute acids. 

To obtain cesculin, Rochleder extracts the 
bark with hot water, precipitates the solution 
with alum and a slight excess of ammonia, 
filters, and evaporates the filtrate to dryness 
at 100°. The residue yields sesculin to hot 
alcohol, when it -may be purified by succes- 
sive crystallisations. Another method (Fair- 
thome, Chem. News, 26, 4) consists in exhausting 
the bark with dilute ammonia, evaporating to 
dryness, mixing the residue with alumina, and 
extracting with 95 p.c. alcohol. The alcoholic 
solution yields crystals of sesculin which are 
purified by washing with water, ether, and 
benzene, ^sculin forms colourless prisma which 
lose water of crystallisation at 120°-130°, and 
melt with decomposition at 160° (Zwenger, 
Annalen, 90, 65), It is soluble in glacial acetic 
acid, acetic ester, and in hot alcohol; very 
slightly soluble in cold watei and nearly in- 
soluble in ether. The aqueous solution has a 
blue fluorescence. Emiilsin or dilute acids 
convert it into oescidetin and glucose (Rochleder 
and Schwartz). Heated with baryta water it 
yields cescidetie acid and glucose (Rochleder, J. 
1856, 678). Sodium amalgam reacts forming 
hydrcescvlin (Rochleder, Zeitsch. Chem. 1868, 
727). A characteristic colour reaction is ob- 
tained by agitating sesculin with nitric acid, 
when a yellow solution results which on the 
addition of ammonia turns deep red (Sonnen- 
schein, Ber. 9, 1182). Concentrated sulphuric 
acid followed by solution of sodium hypochlorite 
strikes a violet colour (Raby, J. Pharm. Chim. 
[v.] 9. 402). 

^aculelin is usually prepared by the action 
of dilute acid on sesculin (Zwenger, Annalen, 90, 
63). It crystallises in shining needles or scales 



containing a molecule of water. It melts with 
decomposition above 270°. It is soluble in- hot 
but only slightly soluble in cold water and 
alcohol, and nearly insoluble in ether. The 
aqueous solution has a slight blue fluorescence. 

By reduction with sodium amalgam, sescule- 
tin yields hydrocesculetin CigHjjOj and cescu- 
letin dihydride CgHjO,. Hydrosesculetin ap- 
pears to be identical with the oescorcin of Roch- 
leder (J. 1867, 761). It is converted by gaseous 
ammonia into dehydrocBSCorcein CuHjjOjNa, a 
deep violet coloured mass, ^sculetin dihy- 
dride, similarly, when treated with ammonia, 
exhibits a striking series of colour reactions, 
^sculetin unites with sodium hydrogen sul- 
phite forming sodium dihydrocesculeiinauVphonate. 
This compound is not decomposed by dilute 
acids ; by the action of gaseous ammonia it is 
converted into the deep violet coloured com- 
pound described by Rochleder as oescorcein 
CbHiOjN, but which is in reality sodium cescor- 
ceinsulphonate CisHi^OieN^SaNaj (Liebermann 
and Wiedermann, Ber. 34, 2608 ; Liebermann 
and Lindenbaum, ibid. 35, 2919). 

The diacetyl derivative of sesculetin has 
been prepared by Gattermann and Kobner (Ber. _ 
32, 287) by the action of sodium acetate and 
acetic anhydrid.e on 2:4:5-trihydroxybenzalde- 
hyde. ^souletin is thus shown to have the 
constitution 

CO 

C8Ha(0H)j< I (OH)j:0:CH=l:2:4:5. 

\CH=CH 

Fraxin crystallises in colourless needles con- 
taining^ half a molecule of water of crystallisation. 
By the action of dilute acids it is converted into 
fraxetin, and glucose (Salm, J. 1869, 676). 
Fraxetin consists of tables (from alcohol) very 
slightly soluble in water, but soluble in ether and 
hydrochloric acid. 

Horse-chestnut cotyledons were found by 
Rochleder (J. pr. Chem. [i.] 87, 1 ; [i.] 101, 415) to 
contain three compounds. Argyrcescin C27H42O] j 
a crystalline glucoside converted by dilute acids 
into glucose and argyroescetin CaiHaoOg, and by 
potash into propionic acid and mscinic acid 
Cj^HjoOj, a compound found ready formed in 
the cotyledons. The third constituent of the 
cotyledons is theglucosideapftrodtEscmCjjHjjOjj, 
which, acted on by potash, also yields ceacinic 
acid, the second product being in this case 
hutyric acid, or when heated with dilute acids 
glucose, and telcescin CuHjoO,. Telsescin acted 
on by hydrochloric acid gas gives up another 
molecule of ffZMCose and forms oBsctVemjiCuHjoOa 
(Rochleder, J. 1862, 491 ; 1867, 761). 

Thd leaves of the horse-chestnut contain the 
glucoside quercitrin CajHajO^o and the flowers 
quercetin CajHisOu (Rochleder, J. 1859, 522). 
Quercitrin is usually prepared from black oak 
bark, Quercus discolor (Ait.) (Liebermann and 
Hamburger, Ber. 12, 1179) and from this com- 
pound by treatment with dilute acids quercetin 
together with isodulcite is obtained. 

For other reactions and the constitution of 
these compounds v. Gltjcosides. 

For examination of horse-chestnuts see 
Laves (Chem. Zentr. 1903, ii. 1133). The oil 
present in them was at one time used in medi- 
cine ; it has been investigated by Stillesen 
(Chem. Zentr. 33, 497). A. S. 



4S 



HORSE-RADISH. 



HORSE-RADISH. The root of CoMeana 
Armoracia (laiul.), used as a condiment. Its 
pungent flavour is due to the presence of 
tsobutyl isothiooyanate, CjHj-NCS. The root 
contains — 

Nitrogenous JT-free Crude Organic 

Water substaaces Fat extract fibre Asli sulphur 
76-7 2-7 0-3 15-9 2-8 1-5 008 

The following is an analysis of the ash of 
horse-radish : — 

Percent, ot _ o <-, o" ■» 

aahinthe "=« «~ <= 'S °- O q" O 
drysubst- MBuafePHm So 

7-1 30-8 40 8-2 2-9 1^ 7-8 30-8 12-7 0-9 

H. I. 

HUMIC ACID. The substance produced by 
the decay of vegetable matter and found in the 
soil. Variouj humio acids have been described ; 
-an ootobasio acid CeoH5402, (Detmer, J. 1873, 
844); an acid CjjHioOio (Thenard, J. 1873, 844) ; 
an acid CjsHjjOio, from brown coal (Hoppe, 
Zeitsch. physiol. Chem. 13, 108) ; and an acid 
CjjHjjOas from coal (John, Zeit. Kryst. Min. 23, 
289). According to Robertson, Irvine, andDobson 
(Bio-Chem. J. 1907, 2, 458), the natural humic 
acid from peat varies greatly in composition, 
according to the method of preparation. The 
artificial acid from sugar, according to them, 
his the composition C,9HjjO,4, but Berthelot 
end Andre (Compt. rend. 112, 916) state that 
this acid istribasio and has the composition 
C] sHjgO,. Humic acid is capable of absorbing 
ammonia, which is then removed by the acid of 
sprouting seeds, humio acid being regenerated 
(Borntraeger, Chem. Zentr. 1900, ii. 1202). 
Gautreau, Charbonnier, and Serrant (Eng. Fat. 
22028 ; J. Soc. Chem. Ind. 1895, 977) treat peat 
or vegetable refuse with dilute sulphurio acid, 
to produce humic acid. The mass after the 
removal of the liquid matter is treated with 
excess of lime, potassium sulphate is added 
and the resulting substance sold as a manure. 

HUNGARIAN TURPENTINE v. OLEO-BBsnis. 

HUNGARY BLUE. CdbcOt blue v. Pigmbnts. 

HUNGARY GREEN. Malachite green v. 
Pigments. 

HYACINTH V. Zircon and Zibconium. 

HYaiNASIC ACID CjAj-COOH, m.p. 77-5°, 
is found as a glyceride in the anal glandular 
pouches of the striped hyaena (Carius, Annalen, 
129, 168). 

HYALINE CORUNDUM v. Altjmdhum. 

/NH-CHj 
WiTiPimom,glycolylcarbamideGO< I 

^NH-CO 
was found together with allantoin in the leaf 
buds of Platanus orientalia (Linn.) (Sohidze and 
Barbieri, Ber. 1881, 14, 1834) ; and also in beet 
juice (v. Lippmann, Ber. 1896, 29, 2652). It is 
prepared (I) by reducing allantoin or alloxanio 
acid with concentrated hydrogen iodide at 100° 
(Baeyer, Annalen, 1864, 130, 158) ; (2) by the 
action of excess of alcoholic ammonia on brom- 
acetylurea at 100° (Baeyer, Ber. 1876, 8, 612) ; 
(3) by the condensation of sodium dihydroxy- 
tartrate and carbamide in the presence of 
hydrochloric acid at 50°-60° (Ansohiitz, Annalen, 
1889, 254, 258); (4) by the condensation of 
glyoxal and carbamide in the presence of hydro- 
chloric acid (Siemonsen, Annalen, 1904, 333, 
101) J (5) from ethyl hydantoate by heating at 



135° for 7 hours, or by warming with 25 p.o. 
hydrochloric acid (Harries and Weiss, Ber. 
1900, 33, 3418), oi by heating with alcoholic 
ammonia at 100° (Harries, Annalen, 1908, 361, 
69) ; the ethyl hydantoate is prepared by the 
condensation of the hydrochloride of thek ethyj 
ester of glycine with potassium cyanate (Harries 
and Weis, l.c.) or by the interaction of glycollic 
ester and ethyl sodiocarbonate (Diela and 
Heintzel, Ber. 1905, 38, 305). 

Hydantoin crystallises in colourless needles, 
m.p. 216° (Schulze and Barbieri, Anschiitz, l.c.) ; 
217°-220° (Harries and Weiss, Z.c.) ; its heat of 
combustion at constant volume is -)-312-4Cal., 
and heat of formation -f-109Cal. (Matignon, 
Ann. Chim. Phys. 1893, [vi. ] 28, 70). Its dissocia- 
tion constant Ka is 7-59x10-" (Wood, Phil. 
Trans. 1906, 1833). lb is sparingly soluble in 
cold, readily so in hot water, and the solution 
has a sweetish taste. Hydantoin is not attacked 
by ammonia, hydrochloric, or dilute nitric acid ; 
when boiled with baryta water it is converted 
into the barium salt of hydantoic acid 

NHj-CONHCHa-COjH, 
the heat of combustion of which is 308-9Cal. 
and heat of formation -|-181-6Cal. (Matignon, 
?.c.). 

The silver derivative 0BH,O2NaAg,H2O is 
precipitated by silver nitrate from. an ammo- 
niacal solution of hydantoin. 

Substituted derivatives of hydantoin are 
^NH-CH, 
referred to the ring COa ? 11 . 
--NH-CO 
/NH-CH(NOj) 

Nltroliydantolll CO<f I . prepared 

^NH-CO 
by the action of nitric acid on hydantoin, ,forms 
shining crystals, melting and decomposing at 
170° (Frauohimont and Klobbie, Eec. trav. 
chim. 1888, 7, 12). 

/NAcCH, 

1 : 3-DiacetylhydantoIn C0< 1 , ob- 

^NAc-CO 
tained by the action of acetic anhydride on 
hydantoin, has m.p. 104°-105°, and yields 

/NAo-CHj 
3-acetylhydantoin C0< I , m.p. 143°-144°, 

^NH-CO 
when boiled with water, and this forms a 
sparingly soluble had aalt (Harries and Weiss, 
Annalen, 1903, 327, 355 ; Siemonsen, Annalen, 
1904, 333, 101). 

/NH-CCIj 

Diehlorohydantoln CO( I or 

^NH-CO 

/NCICH, 
C0\ I obtained in the form of lustrous 

^NCl-CO 
crystalline leaves, m.p. 120°-121° by the action 
of chlorine on an aqueous solution of hydantoin 
(Harries and Weiss, Annalen, 1903, 327, 365; 
Siemonsen, Annalen, 1904, 333, 101 ; Biltz and 
Behrens, Ber. 1910, 43, 1984). Attempts to 
prepare bromibe derivatives of hydantoin have 
been unsuccessful ; by the action of I molecule of 
bromine hydantoin is converted into iaoallituric 

/NH-CH— N— CHj\ 
acid CO^ I 1 >C0, m.p. 258°- 

^NH-CO CO-NH'^ 
260°, when a larger proportion of bromine is 



HYDANTOIN. 



49 



employed, parabanio acid (oxalylcarbamide), is 



foimed, the bromo deiiTative CO' 



•NHCBr, 






being probably first produced. 

Condensation with aldehydes. Hydantoin 
condenses with formaldehyde (1-3 mols.) in 
aqueous solution to form hydroxpnethyl- 

/CHjCO 
hydantoin OH-CHa-NC | 

^CO-NH 

yCOCHj 

or OH-CHj-NC | 

^CO-NH 
m.p. 125°-135°, it yields chloromethylhydantoin 
C,H,OaN,Cl, m.p. 160°-167°, when treated 
with phosphorus pentacbloride or concentrated 
hydrochloric acid. When hydantoin is warmed 
with formaldehyde in the presence of acids more 
complex products are obtained (Behrend and 
Niemeyer, Annalen, 1909, 365, 38). 

Hydantoin condenses with aromatic alde- 
hydes in the presence of glacial acetic acid and 
sodium acetate to form compounds of the type 

/CONH, 
RHC : <y I which, on reduction, yidld 

\nhco 

the corresponding 4-ary2-substituted hydantoin 

<CONH 
I . The following compounds 
NHCO 
are described : — CO-NH 

Benzylidenehydantoin PhHC : C<f I 

^NHCO 
m.p. 220°, yields i-henzylhydantoin {phenyl- 



alaninehydantoin). FhE^i 



CO-NH 



,C-CH< I , 



m.p. 



188°-190° on reduction, from which phenylala- 
nine is obtained by boiling with baryta water (Ru- 
hemann and Stapleton, Phil. Trans. 1900, 246). 
Anisylidenehydantoin 

/CO-NH 
OMe-CjHi-CH : e< ' I 

^NH-CO 
m.p. 243°-244° (deoomp.) yields a bromo 
derivative, m.p. 247° ; and on reduction with 
hydrogen iodide forms i-p-hydroxybenzylhydan- 
toin {tyrosinehydantoin) 

/CONH 
OHC.H,-CHaCH< I 
^NHCO 
m.p. 257''-2SS°, from which tyrosine is obtained 
by prolonged boiling with hydrogen iodide. The 
tyrosinehydantoin, m.p. 275°-280°, described by 
Blendermann (Bied. Zentr. 1883, 209) is probably 
the optically active isomeride of this compound. 
Piperonylidenehydantoin 

<CONH 
I 
NHCO 
m.p. 245°. 

Furfurylidenehydantoin 



^CO-NH 

^ I 
"^NH-CO 



<UU'JNJ 
I 
NH-C( 

icKloro - 4 - hydroxybenzyl 
/CO-NH 
OH-C.Hja.-CH : C< I m.p. 300°, 

\nh-co 



m.p. 232' 

3 ; B-DicKloro - 4 - hydroxybenzylidenehydanloin 
/CO-NH 



Vol. III.— T. 



p-Nitrabenzylidenehydantoin 

/CONH 
NOj-CcHi-CH : C< | 
^NH-CO 
m.p. 254° (Wheeler and HofEmann, Amer. Chem. 
J. 1911, 45, 368). 

Alkyl and aryl substituted derivatives. 
/NH-CH, 
l-MethylhydantoinCOC I by methylating 

\NMeCO 
hydantoin by means of methyl iodide, potassium 
hydroxide, and methyl alcohol at 100° (Franchi- 
mont and Klobbie, Bee. trav. chim. 1889, 8, 
289) ; from methylcarbamide and glycine (Gua- 
resclu, Chem. Zentr. 1892, i. 140); crystallises 
in prisms, m.p. 182°. The nitro derivative 

/N(NOi,)-CH, 
C0< I has m.p. 168° (Franohimont 

\NMe CO. 

and Klobbie, I.e.). 1-p-tolylhydantoin 
NHCO\ 

1 >N-C,H4Me 

CHj-CC^ 

from 2>-tolylcarbamide and glycine (Quenda, 
Chem. Zentr. 1892, i. 140). 

/NMeCHj 
Z-Methylhydantoin C0<^ I prepared 

\nh-co 

(1) by fusing sarcosine and urea (Huppert, Ber. 
1873, 6, 1278 ; Horbaczewski, Monatsh. 1887, 8, 
686) ; (2) by passing cyanogen chloride through 
fused sarcosine (Traube, Ber. 1882,15,2111); 
(3) by heating cafiurio acid with baryta walei 
(Fischer, Annalen, 1882, 215, 286) ; or (4) 'by 
reducing 3-methylallantoin with hydrogen iodide 
(Fischer and Ach, Ber. 1899, 32, 2748) ; forms 
soluble prisms, m.p. 156° ; the silver derivative 
AgCjHjNjOj is crystalline. 

3-Phenylhydantoin from phenylglycine and 
urea has m.p. 191° ; S-tolylhydantoin has m.p. 
210° (Schwebel, Ber. 1877, 10, 2045; 11, 1128). 

Homologues of hydantoin containing the 
substituent in position 4- are most numerous ; 
and are prepared by the following general 
methods : (1) by interaction between the 
cyanohydrin of an aldehyde and carbamide 
(Pinner, Ber. 1887, 20, 2351 ; 21, 2320 ; 22, 
685) ; (2) by the action of dilute hydrochloric 
acid on the hydantoic acid obtained by evaporat- 
ing to dryness a solution of an a-amino acid and 
potassium cyanate (Dakin, Amer, Chem. J. 
1910, 44, 48); or by the interaction of carba- 
mide, the o-amino acid and baryta water 
(Lippich, Ber. 1908, 41, 2953) ; (3) by reducing 
the compound obtained by the condensation 
of hydantoin and an aromatic aldehyde (Wheeler 
and Hofimann, l.c.). 

/NH-CHMe 

i-Methylhydanioin{lactylurea)CO^ I 

\nhco 

(Heintz, Annalen, 1873, 169, 125 ; Urech, Ber. 
1873, 6, 1113), m.p. 140° or 145°. The nitro- 
.NH-C(NOa)Me 



derivative CO^ 



< 



m.p. 



148° 



NH-CO 

(Franchimont and Klobbie, Reo. trav. chim. 
1888, 7, 13). i-isoButylhydanioin 
/NH-CH-C4H8 
C0< I 

\NHCO 
has m.p. 209°-210° (Pinner and Lifschiitz, Ber. 



50 



HYDANTOIN. 



1887, 20, 2351), 212" (Lipploh, ibid. 1808, 41, 
2953). l-i-isoButylhydantoin has m.p. 212°, 
[o]!""— 68-2° in normal sodium hydroxide 

solution, becoming zero in 30 hours owing to 
the enol-keto desmotropy of the group 
CH-CO 5> C : C-OH. 

/NH-CMeEt 
-4 : i-MetJiylethylhydantoin. C0<' I has 

m.p. 172°-173°, and [o]|°+32°, and this is 
constant in normal sodium hydroxide solution 
(Dakin, I.e.). i-Phenylhydahtoin, m.p. 178°; 
the acetyl derivative has m.p. 145° (Pinner, I.e.); 
.NH'CBrPh 



the bromo derivative CO' 



r 



melts 



above 200°, and is decomposed by hot water 
jrtelding i-hydroxy-i-phenylhydanioin (Gabriel, 
Annalen, 1906, 350, 118). i-Oinnamylhydantoin 

/CO-NH 
CHPh:CHCH< I m.p. 171°-172° (Pin- 

^NH-CO 
nei and Spilker, Ber. 1889, 22, 685). i-Ethylhy- 
danioin, m.p. 117°-118°, yields i-hromoethyli- 

/NH-C:CBrMe 
denehydantoin CO^ I m.p. 230°- 

^NH-CO 
236°, on bromination ; the corresponding methyl 
compound yields i-hromomethylenehydanfoin 



CO 



NH'O : CHBr, 



^NH-CO 
m.p. 241'"-242° (Gabriel, Annalen, 1906, 348, 60). 
4 : i.-Dimethylhydantoin (acetonylcarbamide) 
/NH-CMej 



CO 



^NH-CO 



formed by the action of hydro- 



cyanic acid, and cyanic acid on acetone has m.p. 
175° ; the nitro derivative has m.p. 161°- 162° 
(Urech, Annalen, 1872, 164, 264 ; Errera, Gazz. 
chim. ital. 1896, 26, 1, 210) ; 4 : i-diethylhydan- 
toin has m.p. 165°, and 4 : i-dipropylhydantoin, 
m.p. 199° (Errera, i.e.). By the action of 
sodium hypochlorite and free hypochlorous acid 
on 4 ; 4-disubstituted hydantoins, the corre- 
sponding 1 : 2-dichloro compounds 
/Na-CRR' 

C0< I 
^NCl'CO 
are obtained. These compounds can be crystal- 
lised from chloroform, but are decomposed by 
water, alcohol, or hydrogen iodide, regenerating 
the original hydantoin (BUtz and Behrens, Ber. 
1910, 43, 1984). 

1 : S-Diehloro-i : i-diphenylJiydantoin 

CPh.-NCk 

I >co ' 

CO — Nd^ 
has m.p. 164° with decomposition, it yields 
4 : i-diphenyl-1 : 3-dimethylhydanioinvfhentiea,t- 
ed with methyl sulphate. 

1-Methyl-i-phenylhydantoin has m.p. 161°- 
162° (Pinner, Ber. 1888, 21, 2320). i-Methyl-S- 
ethylhydantoin forms volatile plates (BuviUier, 
Bull. Soo. chim. 1895, [iii.] 13, 487). 

3 : i-Dimethylhydanioin has m.p. 120°-121°, 
and yields 3-methyl-i-bromomethylenehydantoin 



CO^ 



NMeC : CHBr 



NH 



• io 



m.p. 143°-144°, by the 



action of bromine (Gabriel, Annalen, 1906, 348, 
50). M. A. W. 

HYDNO-CARPIC ACID, HYPOGALIC ACID, 

V. Oils, Eixed, and Fats. 

HYDRACRYLIC ACID v. Laotio aCid. 
HYDRiESCULIN v. Hoese-ohestnut. 
HYDRARGOL, HYDRARGOTIN, HYDRAR- 
GYROSEPTOL, v. Synthetic deugs. 

HYDRASTINE CsjHsiNO, occurs, together 
with berberine and canadone, in the roots of the 
golden seal {Hydrastis canadensis [Linn.]), a plant 
belonging to the Banuncvlacece and indigenous 
to North America (Durand, Amer. J. Pharm. 23, 
13; Perrins, Pharm. J. May, 1862; Power, 
Jahrb. 1884, 1396; Preund and Will, Ber. 
1886, 19, 2798 ; Linde, Arch. Pharm. 1898, 236, 
696, 698 ; Schmidt, ibid. 232, 136). It was first 
isolated by Durand in 1850, but was obtained 
pure for the first time by Perrins in 1862. 

Preparation. — ^The aqueous or alcoholic 
extract of the root is treated with dilute sul- 
phuric acid to precipitate the berberine, and 
after filtration, the filtrate (if alcohol has been 
used for extracting) is treated with ammonia 
water until nearly neutral, the ammonium sul- 
phUte is filtered off and the liquid after concen- 
tration is mixed with cold water to precipitate 
resinous and oily matter. The filtrate is then 
treated with excess of ammonia water and the 
hydrastine thus precipitated, is recrystallised 
from alcohol or ethyl acetate {see also Freund 
and Will, I.e. ; Ough, Chemist and Druggist, 
1901, 59, 152). 

Properties. — Hydrastine is closely related to 
narootine, of which it is probably a methoxyl 
derivative. Our knowledge of its structure is 
mainly due to the work of _Schmidt and of 
Freund (Annalen, 1892, 271, 311 ; Fritsch, ibid. 
1895, 286, 18 ; Rabe and McMillan, ^^id. 1910, 
377, 223). It forms colourless, almost odourless 
and tasteless 4-sided prisms, which melt at 
132°, to a light amber coloured liquid. It is 
almost insoluble in water but is readily soluble 
in ether, alcohol, chloroform, and benzene. It 
is IsBvorotatory. When oxidised with potas- 
sium permanganate opianic acid is formed 
(Labat, Bull. Soc. chim. 1909, [iv.] 5, 743), and 
when heated with nitric acid at 50°-60°, it 
yields opianic acid and hydrastinine (Freund and 
Will, Ber. 1887, 20, 94), whilst when oxidised 
in alkaline solution, it yields hemipinic and 
nicotinic acids. 

When fused with potash, it yields proto- 
catechuic and formic acids. Hydrastine forms 
a faint yellow solution in sulphuric acid, 
which turns reddish purple on warming and 
which decolorises potassium permanganate. 
With platinum chloride hydrastine gives an 
orange-yellow precipitate ; with gold chloride, _ 
a yeUow-red ; with picric acid, a yellow ; and 
with potassium dichromate, a yellow precipi- 
tate, which turns red on addition of sulphuric 
acid. In contact with a potassium iodide solu- 
tion containing free iodine it yields a brown hexa- 
iodide,orahydriodidepentiodideCj,H2,N08HI'I,, 
(Prescott and Gordin, J. Amer. Chem. Soo. 1899, 
21, 732). 

Hydrastine combines readily with ketones, 
forming condensation products with elimination 
of water (liebermann and Kropf, Ber. 1904, 37, 
211). It also forms similar condensation pro- 
ducts with most compounds containing methy- 



HYDRAZINES. 



51 



lene groups between carbonyl groups and also 
with such compounds as hydroquinone, phloro- 
glucinol, and pyrogallol (Liebermann and Glawe, 
ibid. 2738). When heated with carbamide it 
forms meoonin (Beckurts and Frferiohs, Arch. 
Pharm. 1903, 241, 259). When O'l o.o. of a 
hydrastine solution in alcohol is added to 2 e.c. 
of pure sulphuric acid (sp.gr. 1-84), and 0-1 c.c. 
of a phenolic substance is aaded,'the mixture, on 
warming, develops beautiful colourations. Thus 
with gallio acid the colour is emerald green, 
which gradually becomes blue. With guaiacol 
or catechol, a red colour is produced which turns 
violet, and with morphine the mixture becomes 
violet (Labat, Bull. Soo. chim. 1909, [iv.] 5, 742). 

Hydrastine may be distinguished from most 
other alkaloids ■ by the fact that when a few 
drops of Nessler's reagent are added to a solu- 
tion of its hydrochloride, a precipitate which 
instantly blackens is produced. Only morphine, 
apomorphine, and picrotoxin precipitate mer- 
cury more or less quickly from the reagent 
(Jorissen, Ann. Chim. anal. 1903, S, 127). When 
chlorine is added to the hydrochloride, a blue 
fluorescence appears. 

For the estimation of hydrastine in extract 
and tincture of hydrastis, see Gordin and Pres- 
cott, I.e. ; Maben, Chem. and Druggist, 1901, 
59, 234 ; Matthes and Bammstedt, Arch. Pharm. 
1907, 245, 112 ; Packner, Chem. Zentr. 1908, ii. 
266 ; Boeder, J. Soc. Chem. Ind. 1908, 1037 ; 
Bupp, ibid. 1910, 449, 

Hydrastine and its salts, which form hygro- 
scopic crystalline powders of bitter taste, are 
used in medicine chiefly for external use in the 
treatment of subacute and of chronic inflamma- 
tory conditions of the mucous membrane ; also 
in uterine catarrh and more rarely, internally 
for gastro-intestinal catarrh and catarrhal 
jaundice (Falk, Virchow's Arch. 1895, 142, 
360; Bunge, Chem. Zentr. 1895, i. 1173; 
- Phillips and Pembrey, Proc. Physiol. Soo. 1896- 
7,4). 

Foi the salts and derivatives of hydrastine, 
see Merck,' Chem. Zeit. Eep. 1893, 17, 30; 
Freund, I.e. ; Ber. 1889, 22, 456 ; ibid. 1890, 23, 
404, 416, 2897, 2907; ibid. 1893, 26, 2488; 
Norton and Newman, J. Amer. Chem. Soc. 1897, 
19, 838; Schmidt, Arch. Pharm. 1898, 236, 
334 ; D. R. P. 58394 ; Rabe and McMillan, I.e. 

Hydrastinine CjiHisOjN, which is formed 
by the oxidation of hydrastine with dilute 
nitric acid, can also be prepared by the dry dis- 
tillation, of a mixture of hydrastine and soda 
lime in an atmosphere of hydrogen (Schmidt, 
Arch. Pharm. 231, 541). It forms needle 
shaped crystals, m.p. 116°-117°, and is readily 
soluble in alcohol, ether, and chloroform, more 
sparingly in hot water. When reduced with 
zinc and hydrochloric acid, or when boiled with 
potash, or electrolysed in dilute sulphuric acid, 
it forms ht/drohydrastinine, m.p. 171° (Freund; 
Bandow and Wolfenstein, Ber. 1898, 31, 1578). 
Oxidised with nitric acid, it yields apophyllio 
acid. By the continued oxidation of hydra- 
stinine with potassium permanganate, hydra- 
stinic aeid CiiHjNOj, m.p. 164° (decomp.), is 
obtained in fine wmte needles. Hydrastinic 
acid when boiled with nitric acid, yields a 
crystalline substance, CioH,NOi, m.p. 233°, 
which, on boiling with potash, yields hydrasiie 
aeid, m.p. 176°, a dibasic acid which readily 



forms an anhydride (Freund, Ber. 1889, 22, 
1156, 2322, 2329; Annalen, 1892, 271, 375; 
Perkin, Chem. Soc. Trans. 1890, 1095; Perkin 
and Robinson, ibid. 1907, 1086). 

Hydrastinine hydrochloride, m.p. 212° (de- 
comp.), forms a light yellow granular or crystal- 
line deliquescent powder. It is odourless, has a 
bitter saline taste, is very soluble in cold and 
hot water and alcohol, and is said to be an 
efficient oxytoxio. It has also been recom- 
mended in the treatment of uterine hsemorrhage 
(Merck, J. Soo. Chem. Ind. 1892, 645). 

HYDRAULIC CEMKNTS v. Cbmbnts. 

HYDRAULIC LIME v. Cements. 

HYDRAZINES. The name ' hydrazine ' was 
applied by Emjl Fischer to the then unknown 
dlamide H^N-NH^, ' which he regarded as the 
parent substance of the hydrazines, a large and 
important class of bases which had been pre- 
pared by him and the reactions of which showed 
them to possess a structural formula derived 
from diamide by the replacement of one or two 
hydrogen atoms by hydrocarbon radicles. • The 
name was intended to indicate the connection 
of these compounds with the azo and diazo 
compounds and particularly with hydrazoben- 
zene, CeH5-NH-NH-C,H5, the oldest known 
member of this class, which itself may be re- 
garded as a symmetrically dlsubstituted hydra- 
zine. 

It is apparent that there are five different 
ways in which the four hydrogen atoms of 
diamide may be replaced by hydrocarbon radi- 
cles, thus: (1) RNH-NHj, (2) RRN-NHj, 
(3) RHN-NHR, (4) RRN-NHR, (5) RRN-NRE, 
but the name hydrazine was formerly only 
applied to those derivatives of diamide which 
had the hydrocarbon radicle or radicles asym- 
metrically attached to the molecule, that is to 
say, those which are constituted in accordance 
with formulee (1) and (2). 

This was mainly owing to the fact that the 
compounds constituted as in formula (3) had 
already been named, as for example, hydra- 
zobenzene, CjHjNH-NH-CjHj, and that no sub- 
stances of the formulae 4 and 5 had as yet been 
prepared. At the present time compounds of 
all five classes are known, and therefore the name 
hydrazine is applied to all derivatives of 
diamide. 

The hydrocarbon radicles forming the hydra- 
zines may belong either to the aliphatic or 
aromatic series, although the most important 
members of the group belong to the aromatic 
series. Like the amines, they are divided into 
primary and secondary hydiazines, according 
as one or two hydrocarbon radicles are con- 
tained in them; that is to say, the primary 
hydrazines are constituted as in formula (1), the 
secondary hydrazines as in formula (2). The 
secondary hydrazines may be symmetrical dr 
asymmetrical as in formula (2) or (3) : com- 
pounds constituted as in formula (4) are tertiary 
hydrazines, whilst quarternary hydrazines have 
a structure represented by formula (5). 

General metJwds of preparation. — The primary 
and secondary hydrazines can be considered as 
being derived from the primary and secondary 
amines respectively by the replacement of one 
of the hydrogen atoms attached to the nitrogen 
by the primary amino group — 
RNHH -> RNH-NHj, RRNH -> RRN-NH, 



HYDRAZINES. 



These compounds are therefore prepared from 
the primary and secondary amines through the 
agency of nitrous acid. , 

Since the primary aromatic amines yield 
diazonium salts when treated with nitrous acid, 
these salts are always intermediate products in 
the formation of the primary aromatic hydra- 
zines and are converted into them by the action 
of reducing agents. Tor general purposes this 
reduction may be effected in one of two ways — 

(1) By the reduction of the solution of the 
diazonium salt by stannous chloride (Y. Meyei 
and Leoco, Ber. 1883, 16, 2976)— 

0,H5-Nsa+4H=C,Hj-NH-NHj,Ha 

(2) By treating the diazonium salt with 
alkiili sulphite, in order to prepare the alkali salt 
of the sulphonic acid, and then by reducing this 
with zinc dust and acetic acid to form the alkali 
salt of the hydrazine sulphonic acid thus — 

C,H5-NjS03K+2H=C,Hj-NH-NH-S03K. 
Finally, by boUing this salt with hydrochloric 
acid to convert it into the hydrochloride of the 
hydrazine and potassium hydrogen sulphate 
(B. Fischer, Annalen, 1877, 190, 71 ; Eeychler, 
1887, 20, 2463). 
CsHt'NH-NH-SOaK+HjO+HCl 

=C5H5-NH-NHj,Ha+KHS04. 
These reactions can only be applied to the 
aromatic amines because those of the aliphatic 
series do not form diazonium salts. 

Primary aliphatic hydrazines have, however, 
been prepared by B. Fischer (Ber. 1884, 2841 ; 
Annalen, 1877, 199, 281) from the symmetrical 
dialkyl ureas by transforming them into their 
nitroso derivatives by the aid of nitrous acid and 
then by converting the hydrazinureas, formed 
from these on reduction, into the primary 
hydrazines by the action of fuming hydrochloric 
acid. 

RHN-CO-NHE+NOOH = RHN-CO-N(NO)R 
RHN-C0-N(N0)R+4H 

=RHN-Cd-N(NHj)R+H,0 
RHN-CO-N(NHa)R+H,0 

=COj+(NHj)NH-R+NH,-R. 
Primary hydrazines of the aromatic series are 
also formed when certain diazoamino compounds 
are reduced in alcoholic solution with zinc dust 
and acetic acid. Thus diazoaminobenzene 
passes in this manner into phenylhydrazine 
(E. Fischer, Annalen, 1887, 90, 77). 
C,H5-N2-NH(C.H5)+4H 

=C5H5-NH-NHj+C,H5NHjj. 

The secondary hydrazines both of the aro- 
matic and aliphatic series are prepared from the 
corresponding secondary amines. The amines 
are converted into their nitroso derivatives, by 
the aid of nitrous acid, which are then trans- 
formed into the hydrazines by reduction. 
R2lSIH-fNOOH=RjN-NO+H.O 
RsN-NO+4H=R2N-NH+H,0. 

Phenylhydrazine CjHj-NH-NHa, the most 
important member of the hydrazine group, can 
be prepared by either of the methods mentioned 
above. 

(1) From aniline by the aid oj stannous 
chloride. Ten grams of aniline are dissolved in 
100 grams of concentrated hydrochloric acid 
and the semi-solid mass of aniline hydrochloride 
is then cooled, externally, by means of ice. 
A solution of 10 grams of sodium nitrite 



dissolved in 60 c.c. of water is then gradually 
added until a test portion diluted with water 
shows, by means of starch and potassium 
iodide paper, the presence of excess of nitrous 
acid. The solution of benzene-diazonium chlo- 
ride formed in this manner is then treated 
with a solution of 60 grams of stannous 
chloride dissolved in 60 c.c. of concentrated 
hydrochloric acid, the reducing agent being 
cooled by means of ice and added gradually 
with constant stirring to the solution of the 
diazonium salt. After standing for one hour, the 
phenylhydrazine hydrochloride is filtered at the 
pump, dissolved in water and converted into 
the free base by the addition of excess of aqueous 
caustic potash. The liberated base is extracted 
with ether, dried by potassium carbonate and 
purified by distillation under diminished 
pressure. 

(2) From aniline by the aid of sodium sul- 
phite. A solution of 60 grams of aniline in 
2J molecules of hydrochloric acid and 300 c.c. 
of water is diazotised by the addition of the 
calculated quantity of sodium nitrite solution, 
and is then mixed with a cold concentrated 
aqueous solution of 2| molecules of sodium sul- 
phite. The whole is then genUy warmed on the 
water bath and treated with zinc dust and a 
little acetic acid until colourless, when it is 
heated to the boiling-point and filtered, whilst 
hot, from the unchanged zinc. One-third of its 
volume of concentrated hydrochloric acid is 
then added to the hot solution and the phenyl- 
hydrazine hydrochloride, which separates on 
cooling, is removed by filtration and treated 
in the same manner as in the previous prepara- 
tion. 

For the preparation of phenylhydrazine and 
its derivatives from urea and substituted ureas 
by the action of alkaline hypobromites, 
cp. Schestakow, D. R. P. 164765 : Patentol. 26, 
1869. 

Tertiary aromatic hydrazines of the general 
formula RNH-NE, may be prepared by the 
interaction of j3-aryIhydroxylamine and mag- 
nesium halogen aryl (Busch and Hobein, Ber. 
1907, 40, 2099). Thus triphenylhydrazine 
0,H5NH-N(C8H5), is formed when phenyl- 
magnesium bromide reacts with jB-phenyl- 
hydroxylamine. The corresponding quaternary 
hydrazine tetraphenylhydrazine 

(C.H,),N-N(C.H.), 
has been prepared by C!hattaway and Ingle 
(Trans. 1895, 67, 1090) by the action of iodine 
on the sodium compound of diphenylamine, and 
by Weland and Gambarjan (Ber. 1906, 39, 
1501) by the oxidation of diphenylamine. 

Certain compounds belonging to the group of 
the dihydiazines have been prepared by V. 
Braun (Ber. 1908, 41, 2169; ibid. 2604; 1910, 
1495), and are recommended as reagents for 
compounds containing carbonyl oxygen. Thus 
diphenylmethandimethyldihydrazine 
[NH8-N(C!H3)C.HJ,CH, 
is prepared by condensing methylam'line with 
formaldehyde to give p-dimethyldiaminodi- 
phenylmethane [HN(CH,)C,H,]jCHj, the ni- 
troso compound of which gives the dihydrazine 
on reduction with zinc and acetic acid. 

Properties and reactions ol the hydrazines. 
The primary aromatic hydrazines are mono- 



HYDRAZINES. 



S3 



acid bases which form well-defined, stable salts 
with both mineral and organic acids. Unlike 
the corresponding aliphatic primary hydrazines 
they do not form salts containing two equiva- 
lents of a mono-basic acid. The secondary 
aromatic hydrazines are also mono-acid bases 
but their salts are partially decomposed by water. 
The primary aromatic hydrazines, for example 
phenylhydrazine, react with metallio sodium 
forming a sodium compound from which alkyl 
derivatives can be prepared by the action of 
alkyl iodides — 

. C,H5-NNa-NH,+RI=OoHs-NR-NHj+NaI 
(cp. MichaeUs, BeA 1886, 19, 2448; 1887, 20, 
43 ; also Annalen, 1889, 252, 267). The pure 
so(^um compound can be prepared by acting on 
sodamide with a dilute benzene solution of 
phenylhydrazine (Titherley, Ohem. Soo. Trans. 
1897, 71, 461)— 

NaNHj-hO„H5-NH-NH2=CsH5-NNa-NHj+NH3 
The corresponding potassium salt may be 
obtained as large colourless rhombic crystals 
when phenylhydrazine is treated with a satu- 
rated alcoholic solution of potassium hydroxide 
in the absence of air (Chattaway, Chem. Soc. 
Trans. 1907, 91, 1326), 

The primary hydrazines are readily afEected 
by oxidising agents and are consequently strong 
reducing agents. Phenylhydrazine reduces Feh- 
'ling's solution in the cold, even in very dilute 
solution, a reaction which distinguishes this 
compound from the secondary base, diphenyl- 
hydrazine, which reduces Fehling's solution only 
on warming. (For the behaviour of phenyl- 
hydrazine on oxidation, cp. Fischer, Annalen, 
1878, 190, 67; 1879, 199, 281; Fischer and 
Ehrhard, Annalen, 1879,-^199, 333; Haller, 
Ber. 1885, 18, 90; Zinoke, ibid. 1885, 18, 786; 
Straehe, Monatsh. 1891, 12, 623 ; 1S92, 13, 316; 
. Murster, Ber. 1887, 20, 2633.) 

The original statement by Fischer that the 
oxidation of phenylhydrazine by mercuric oxide 
leads to a partial production of the diazonium 
salt has been modified by Chattaway (Ohem. Soc. 
Trans. 1908, 93, 270), who finds that diazonium 
salts are not produced when the action is carried 
out in alkaline solution but only in the presence 
of a large excess of strong acid. Azoimidcs are 
formed when alkali is absent and the hydrazines 
are present in excess. The quantitative con- 
version of phenylhydrazine into benzenedia- 
zonium chloride may be effected by dissolving 
the hydrazine in glacial acetic acid, cooling the 
solution to about —16° by the addition of 
crushed ice and either by passing in a rapid 
stream of chlorine or (if the diazonium bromide 
is desired) adding the calculated quantity of 
bromine dissolved, in acetic acid and similarly 
cooled by ice. The reaction evidently proceeds 
in accordance with the scheme 



C,Hb-NH 

I 
H-NH 



CeH,-NCl 
H-Na 



CeHj-Na 

III 
N 



(Caiattaway, Chem. Soc. Trans. 1908, 93, 863). 

The mechanism of the reaction involved in 
the oxidation of phenylhydrazine either by 
oxygen or an oxidising agent, is explained in 
the following way (Chattaway, Trans. 1908-, 93, 
270) :— ,? 

In the first instance, one of the hydrogen 



atoms of the hydrazino group is attacked and a 
hydroxyhydrazine is produced 

RNH-NHj-fO=RNH-NH(OH). 
This substance, however, not being stable in 
the presence of alkali, undergoes disruption in 
accordance with the scheme 

R-NH R N H 

I =1+111+1 

H-N-OH H N OH 

the splitting off of the hydrocarbon and water 
occurring in either one or two stages. 

If, however, a very energetic oxidising agent 
is used, a certain number of molecules may, 
before breaking down, undergo a further 
oxidation thus : — 

R-NH R N H 

HO-NOH OH N OH 
yielding a phenol and free nitrogen. In the 
absence of alkali, which acts as a catalytic agent 
and much accelerates the decomposition of these 
hydroxyhydrazines, the introduction of the 
second hydroxyl group takes place to a much 
greater extent and in the presence of strong acid 
and at a low temperature a, diazonium salt is 
formed thus — 

R-NH R-NCl 

I +Ha-^ 111 -f2H20. 

HO-NOH N 

The oxidation of phenylhydrazine by basic 
metallic oxides leads to the formation of the 
free metal. The following process is recom- 
mended for producing a film of metallic copper 
on glass vessels (Chattaway, Chem. Soc. Trans. 
1908, 93, 275 ; see also Proc. Roy. Soc. 1908, 
A, 80, 88). One part of freshly distilled phenyl- 
hydrazine and 2 parts of water are heated until 
a clear solution is obtained, when it is mixed 
with about half its bulk of a warm saturated 
solution of oupric hydroxide in strong ammonia. 
Nitrogen is freely evolved during the addi- 
tion, and the cuprio hydroxide is reduced to 
cuprous hydroxide, which remains dissolved in 
the ammoniacal liquid and does not undergo 
any immediate further reduction. A hot 
10 p.c. solution of potassium hydroxide is then 
added until a slight permanent precipitate of 
cuprous hydroxide is produced and the clear 
liquid is then cautiously heated in contact with 
a perfectly clean glass surface. Metallic copper 
is deposited on it in the form of a thin reflecting 
coherent lamina. To obtain a film of sufficient 
thickness, it is best not to pour ofE the warm 
reducing fluid but to allow it to remain in 
contact with the glass until cold. When the 
liquid is poured ofi,the film of copper should 
be well washed with water and afterwards with 
alcohol and ether. It should then be protected 
by one or two coats of quickly drying varnish. 

When phenylhydraaine is oxidised with 
copper sulphate or ferric chloride, the parent 
hydrocarbon is formed and the whole of the 
nitrogen is eliminated in the free state (Haller, 
Ber. 1885, 18, 90 ; Zincke, aid. 786)— 
C.H.-NH-NHj+CuSOj+HsO 

=CeH,+CuaO+N,+2H,SOj. 

This reaction can be used as a means of 
estimating phenylhydrazine by measuring the 
amount of nitrogen evolved (Gallinek and V. v. 
Richter, Ber. 1885, 18, 3177 ; Straehe, Monatsh. 



Hi 



HYDBAZINES. 



1891, 12, 524 : Straohe and Kitt, ibid. 1892, 13, 
316). (For other methods of estimating hydra- 
zines, cp. Deuigfes, Ann. Chim. Phys. 1895, [vii.] 
6, 381 ; Causse, Cbmpt. rend. 1897, 125, 712, 
and Forster, Chem. Soo. Trans. 1898, 74, 792.) 

Phenylhydraziue also reacts with hydrogen 
peroxide, yielding benzene together with some 
diazobenzeneimide ; it moreover acts as a strong 
reducing agent towards nitro compounds, re- 
ducing them to the corresponding amino 
derivatives (Barr, Ber. 1887, 20, 1498). (For 
the reduction of nitro compounds, cp. also 
Walter, J. pr. Chem. 1896, [ii.] 53, 433. Reduc- 
tion of 1 : 5-dinitroanthraquinone, Schmidt and 
Gattermann, Ber. 1896, 29, 2941. Reduction 
of nitro derivatives of phenanthraquinone, 
Schmidt and Kampf, Ber. 1902, 35, 3124. 
Reduction of hydroxyazo compounds, Oddo 
and Puxeddo, Ber. 1905, 38, 2752. Reduction 
of S-nitrosalicylic acid, Puxeddo^ Gazz. chim. 
ital. 1906, 36, ii. 87.) The hydrazines resist the 
action of reducing agents but pass on protracted 
treatment with zinc dust and hydrochloric acid 
into aniline and ammonia (E. Fischer, Annalen, 
1887, 239, 248) 

C,H5-NH-NHs-f2H=CeH5-NHj-FNH8. 

Primary hydrazines yield with nascent nitrons 
acid in ice cold solution unstable nitroso deriva- 
tives which pass into diazo-imides and water, 
when warmed with alkali — 

C.H,-N<Jg»=CeH,-N<^ -|-H,0. 

The diazoimide is formed directly if the 
above reaction is carried out at a higher tempera- 
ture (E. Fischer, Annalen, 1877, 190, 89, 158, 
181). Phenylhydraziue yields tsodiazobenzene 
salts with amyl nitrite in the presence of sodium 
or potassium ethoxide (StoUe, Ber. 1908, 41, 
2811). The primary aliphatic hydrazines are 
hygroscopic liquids readily soluble in water 
and which possess a smell resembling that of 
ammonia. The aromatic primary hydrazines 
are usually solids at the ordinary temperature. 
They possess a faint aromatic smell and are only 
sparingly soluble in water. 

Phenylhydrazine CcHj-NH-NHa when 
freshly distilled is a practically colourless, highly 
refracting oil which distils under diminished 
pressure without decomposition, or at 240° -241° 
(780 mm.) with slight evolution of ammonia. 
When cooled it sets to a mass of tabular mono- 
jlinic crystals which melt at 17-5°. According 
to E. Fischer (Ber. 1908, 41, 73), the melting 
point of phenylhydrazine is 19-6°, after the 
substance has been purified first by fractional 
distillation at 15-20 mm., then by solidification 
and removal of the liquid portion, an operation 
repeated four times, then by recrystaUisation 
from anhydrous ether, and finally by distillation 
under a pressure of 0-5 mm. For ordinary 
purposes it is sufficient to crystallise the base 
once or twice from its own volume of pure ethej 
and then distil under a pressure of 10-20 mm. 
The base should be coloured pale yellow' and 
should dissolve in 10 times its volume of a mix- 
ture of 60 p.c. acetic acid (1 part) and water 
(9 parts)._ Phenylhydrazine is rather less 
volatile with steam than aniline and rapid^ 
becomes brown when exposed to the air. It 
has a 8p.gr. of 1-097 at 23°. The base is 



sparingly soluble in water but forms a hydrate 
of the formula 2(C,HB-NH-NHs),HaO which 
melts at 24'1°. It is almost insoluble in con- 
centrated aqueous caustic alkali, but is very 
readily soluble in certain alkaline salts, such aa 
the alkali salts of the sulphinic and sulphonic 
acids, soaps, . &c. (Otto, Ber. 1894, 27, 2131). 
For some time it has been prepared on the 
large scale from diazotised aniline by the 
sulphite method, and is used commercially for 
the production of antipyrine, &c., and in the 
form of its sulphonic acid for the production of 
the so-called tartrazine colouring matters. 
Phenylhydrazine is a valuable reagent in organic 
chemistry, owing to the ^se with which it 
forms crystalline compounds with substances 
containing carbonyl oxygen. These compounds, 
which belong to the class of the hydrazones and 
osazones, are dealt with elsewhere {see Hydra- 
zones). 

When taken internally phenylhydrazine 
acts as a violent poison, and when brought in 
contact with the skin causes painful infiamma- 
tion. Chemists who work much with this sub- 
stance usually suffer from ill health, of which 
the most prominent feature is a kind of eczema. 
It seems to form a definite green compound with 
the blood to which the name hmmoverdin has 
been given (cp. Lewin, Compt. rend. 1901, 133, 
599 ; Zeit. Biol. 1901, 42, 107). 

Of the salts of phenylhydrazine, the hydro- 
chloride C,H5-NH-NHj,Ha is the most im- 
portant. It crystallises as colourless glistening 
leaflets which dissolve readily in hot water but 
separate from the solution on cooling. It can 
be recrystallised from alcohol and by careful 
heating can be sublimed unchanged. Other 
aromatic hydrazines of importance are — 

Diphenylhydrazine (CbHs)jN-NH2. This 
compound is produced by the reduction of 
nitrosodiphenylamine (C8H5),N-NO, which is 
obtained from diphenylamine (OjH5)2NH by 
the action of nitrous acid (E. Fischer, Annalen, 
1877, 190, 174 ; Stahel, ibid. 1890, 258, 242 ; 
Overton, Ber. 1893, 26, 19). It forms colourless 
plates which melt at 34 -5° and is partially de- 
composed on distillation under diminished 
pressure. The hydrazine yields well-defined 
crystalline compounds with sugars and can be 
used for the quantitative estimation of arabinose 
(Neuberg and Wohlgemuth, Ber. 1894, 27, 
3106). 

Methylphenylhydrazine CeH8(CH,)N-NHs 
may be prepared either by the reduction of the 
nitroso compound C8H5(CH3)N-NO (E. Fischer, 
Annalen, 1877, 190, 150), or by the alkylation of 
sodium phenylhydrazine by means of methyl 
iodide (A. Michaeh's, Ber. 1.886, 19, 2450; 
Phillips, ibid. 1887, 20, 2485). It is a colourless 
liquid, boiling with slight decomposition and 
evolution of ammonia at 227° (745 mm.) ; 
under a pressure of 75 mm. it boils without 
decomposition at 131°. Methylphenylhydrazine 
is a valuable reagent for the isolation of certain 
ketones (Neuberg, Ber. 1902, 35, 959). 

Phenylbenzylhydrazine 

C,Hj(CH2-CeH5)N-NHj 
(Ofner, Monatsh. 1904, 25, 593) is prepared by 
the direct action of bpnzyl chloride on phenyl- 
hydrazine and is a colourless liquid boiline at 
216°-218° at 38 ihm. It is a useful reagent foi 



HYDRAZINES, 



S5 



the isolation of the sugars, as the hydrazones 
formed from it are less soluble and more easily 
produced than those from simpler hydrazines 
(cp. Euff and Ollendorf, Ber. 1899, 32, 3255; 
liobry de Bruyn, Reo. trav. chim. 15, 91, 227). 

p-Bromophenylhydrazine HaN-NH-CstiiBr 
may be prepared by brominating phenylhydra- 
zine hydrochloride in the presence of a large 
excess of strong hydrochloric acid (Neufeld, 
Annalen, 1888, 248, 94 ; L. Michaelis, Ber. 1893, 
26, 2191). It crystallises from hot watei as 
long needles which melt at 107° and is a useful 
reagent for the characterisation of sugars. It 
has been used for the preparation of hydrazones 
from certain naturally occurring ketones, as for 
example camphor (Tiemann and Kruger, Ber. 
1895, 28, 1756 ; Tiemann, ibid. 2191). 

Phenylhydiazine-p-sulphonic acid 
C,H4(S0sH)NH-NHj, 
is of historical interest as being the first deriva- 
tive of hydrazine to be prepared, and was ob- 
tained from diazotised p-amidobenzenesulphonic 
acid by reduction with sodium hydrogen sulphite 
(Streoker and Bomer, Ber. 1871, 4, 784 ; Romer, 
Zeitsoh. Chem. 1871, 482). It may be prepared by 
the direct sulphonation of phenylhydrazine and 
when pure crystallises as glistening needles con- 
taining i a molecule of water of crystallisation. 
It is prepared on the large scale from p-sul- 
phanilic acid by diazotisation and reduction 
with sodium sulphite, and is used for the pro- 
duction of the tartrazine colouring matters 

iq-v.). 

p-Niirophenylhydrazine CeH4(N0s)NH-NHi,. 
This substance is recommended by Bamberger 
(Ber. 1899, 32, 1806) for the investigation of 
aldehydes and ketones as being more stable than 
j)-bromophenylhydrazine. It is prepared from 
the sodium salt of 'p-nitrophenylhydrazinesul- 
phonic acid by the action of concentrated 
hydrochloric acid (Purgotti, Ber. 1892, 25, 
119 ; Bamberger and Stemitzki, ibid. 26, 1306), 
and also by boiling the potassium salt of p- 
nitrophenylhydrazinedisulphonio acid with dilute 
hydrochloric acid (Hantzsch and Borghaus, Ber. 

1897, 30, 91). It may also be prepared from 
p-nitraniline by diazotisation and reduction. 
The base forms orange red leaflets and needles 
from hot alcohol, which melt with decomposition 
at 157°. (For the use of this base in the prepara- 
tion of hydrazones of the aldehydes and ketones, 
cp. Bamberger, Ber. 1899, 32, 1806; Hyde, 
ibid. 1810.) 

The naphthylhydrazines. Both the a- and 
/S-naphthyliydrazines can be used for the 
preparation of hydrazones from compounds con- 
taining carbonyl oxygen, but the i8- compound 
is especially recommended by Hilger and Rothen- 
fussei (Ber. 1902, 35, 2627) foe the isolation of 
numerous sugars. The two bases are prepared 
in a similar manner from the corresponding 
diazonaphthalenes on reduction with stannous 
chloride, ot by heating the naphthol with 
hydrazine hydrate at 160° (Hoffmann, Ber. 

1898, 31, 2909). o-Naphthylhydrazine forms 
leaflets from water which melt at 116°-117° and 
boil almost without decomposition at 203° 
(20 mm.) (Knorr, Ber. 1884, 17, 651). ;8- 
Naphthylhydrazine forms glistening leaflets 
from water which melt at 124°- 125° {cp. also 
Franzen, Ber. 1905, 38, 266). 



Hydrazine and some op its Derivatives 

USED AS REAQENTS FOR THE ISOLATION 

OB Aldehydes and Ketones. 

Hydrazine HjN-NHa. This substance was 
first prepared by Curtius by the action of hot 
dilute acids on triazoacetic acid (Ber. 1887, 20, 
1632). It has since been obtained by other 
methods of which the more important are 
(1) from aminoguanidine H2N-C(NH)NH-NH, 
on treatment with caustic alkali (Thiele, 
Annalen, 270, 1). (2) From sodium hypo- 
chlorite and ammonia (Raschig, D. R. PP. 
192783, 198307; Chem. Zentr. 1908, i. 427, 1957). 
(3) From dichlorocarbamide (Chattaway, Chem, 
Soc. Trans. 1909, 95, 237). The last-named pre 
paration is carried out in the following way : — 

Dichlorocarbamide NHCI-CO-NHa (Chat- 
taway, Chem. Soc. Trans. 1909, 95, 465). Six 
grams of carbamide are dissolved in 60 c.c. of 
distilled water and 10 grams of finely divided 
zinc oxide are added. The mixture is cooled to 
about —5° in a freezing mixture and a rapid 
stream of chlorine passed through the liquid. 
If' the operation is carried out in a small flask, 
and this is well shaken in the freezing mixture 
during the passage of the gas, the temperature 
does not rise above zero. The zinc oxide quickly 
dissolves and a clear liquid results, from which 
in a short time crystals of dichlorocarbamide 
begin to separate. When the liquid has become 
a thick pulp from the separated solid and crystals 
no longer appear to separate, the dichloro- 
carbamide is rapidly collected at the pump, 
washed twice with 5 c.c. of ice-cold distilled 
water and then several times with chloroform. 
The yield is 77-5 p.o. of the theory. 

p-Urazine. This substance is formed by 
the elimination of hydrogen chloride from two 
molecules of monochlorocarbamide, which may 
be regarded as the initial product formed by the 
action of ammonia on dichlorocarbamide — 



-NHCl 



H,N- 



co<Sr + cfriS>oo 



co<|i-^H. 



:>C0 



NH. 
p-tTrazine. 

the condensation is therefore effected by the 
action of ammonia (Chattaway, Chem. Soo. 
Trans. 1909, 95, 237). Crude dichlorocarbamide 
free from all adhering mother-liquor is dissolved 
in from 10 to 20 times its weight of water and 
rapidly added to excess of strong ammonia, the 
mixture being thoroughly stirred. A vigorous 
evolution of nitrogen takes place and a white 
crystalline powder separates ; a little more crystal- 
lises out on keeping and a still further small 
quantity on evaporating the mother-liquor afteu 
neutralising with hydrochloric acid. 

Hydrazine sulphate. When ji-urazine is 
mixed with about 6 times its weight of concen- 
trated sulphuric acid and warmed to about 80°, 
it dissolves apparently without change ; on 
heating the solution to about 95°- 100°, hydro- 
lysis slowly takes place with evolution of carbon 
dioxide. On raising the temperature still 
liigher, the rate of evolution of carbon dioxide 
increases, until, at about 120°-130°, it is very 
rapidly liberated ; at this temperature, hydro- 
lysis is soon complete and a clear colourless 
liquid is obtained which deposits crystals of 
hydrazine sulphate on cooling. It is best. 



66 



HYDRAZINES. 



however, to add to the cooled liquor its own 
bulk of water, when pure hydrazine sulphate at 
once separates as a white crystalline powder. 

Free hydrazine has been prepared by Lobry 
de Bruyn (Ber. 1895, 27, 3085) by the action of 
sodium methoxide in methyl alcohol on hydra- 
zine hydrochloride, and also by heating the hy- 
drate NjH^.HjO with barium oxide at 100°. 
It is a very stable liquid which boils without 
decomposition ait 113-5° (761 mm.), and at 56° 
(71 mm.). It solidifies when cooled below 0°, 
and then melts at 1-4°. It has a sp.gr. of 1-003 
at 23° (cp. Easohig, Ber. 1910, 43, 1927). 

Hydrazine hydrate NgH^HjO is the form in 
which hydrazine is liberated from its salts by 
the action of aqueous alkalis. It is a strongly 
refracting, almost odourless liquid, which boik 
without decomposition at 118-5° (739-5 mm.) 
and solidifies when placed in a mixture of solid 
carbon dioxide and ether, but melts again below 
—40°. It ia advisable when preparing this 
substance to employ a silver retort and to avoid 
the use of rubber connections, as the hydrate, 
when hot, attacks glass strongly and quickly 
destroys cork and Tubber. 

Semlcarbazide H,N-CO-NH-NHa. This sub- 
stance was first used for the preparation of 
derivatives of ketones by Baeyer acting on the 
suggestion of Thiele (Ber. 1894, 27, 1918), the 
compound having been prepared earlier in the 
year by Thiele and Strange (Ber. 1894, 27, 31 ; 
Anualen, 1894, 283, 19), who obtained it by the 
action of potassium cyanate on hydrazine sul- 
phate, and by Curtius and Heidenreich (Ber. 
1894, 27, 56), who prepared it by the inter- 
action of hydrazine "hydrate and urea. Seml- 
carbazide may be conveniently prepared in the 
following way : 225 grams of nitrourea in 1700 o.c. 
of concentrated hydrochloric acid are mixed at 
0° with excess of zinc dust and are then left for 
a short time after all action has subsided. The 
filtered solution, after being saturated with 
sodium chloride, is treated with 200 grams of 
sodium acetate and 100 grams of acetone. The 
acetonesemicarbazone zinc chloride, whiph 
separates after some time, is washed with salt 
solution and decomposed by strong ammom'a 
(350 c.c. to 200 grams of the compound) (Thiele 
and Heuser, Annalen, 1895, 288, 312). 

Semicarbazide crystallises from absolute 
alcohol as prisms which inelt at 96°. It readily 
reacts with substances containing carbonyl 
oxygen, in accordance with the scheme 

HoN-CO-NH-NHj+OCR, 

=H2N-C0-NH-N : CRj-fHjO 

forming semicarbazones which possesses the ad- 
vantage of being readily decomposed into their 
components on treatment with dilute acids. 
The method recommended by Baeyer (Ber. 
1894, 27, 1918) for the preparation of a carba- 
Eone is as follows : — 

Semicarbazide hydrochloride is dissolved in 
a little water and the requisite amount of alco- 
holic potassium acetate together with the ketone 
are added, as weU as sufficient alcohol and 
water to eSect complete solution. The length 
of time required for the reaction depends on 
the nature of the ketone and varies from a few 
minutes to 4-6 days ; it is finished when the 
addition of water precipitates a crystalline solid. 
Semicarbazide is usually met with in the form 



of its hydrochloride. The free base slowly 

alte~rs on keeping. _ 

Thiosemlcarbazide NHj-CS-fTH-NH,. Thw 
substance, like semicarbazide, reacts with com- 

Sounds containing carbonyl oxygen in accor- 
ance with the equation — 
HoN-CS-NH-NHa-t-OCRj 

' =HjN-C!S-NH-N : CR,-fH,0 . 

forming thiosemicarbazones, which possess the 
property of forming insoluble salts with the 
heavy metals from which the ketone or aldehyde 
can be readily regenerated (Neuberg and 
Neimann, Ber. 1902, 2049). 

The base can be prepared from hydrazine 
sulphate in the following maimer (Freund and 
Schander, Ber. 1896, 29, 2501; Freund and 
Imgart, ibid. 1895, 28, 948). 60 grams of 
hydrazine sulphate and 27 grams of anhydrous 
potassium carbonate are dissolved in 200 c.c. of 
water and mixed with 40 grams potassium thio- 
oyanate. The mixture is boiled for some minutes 
and is then treated with 200-300 c.c. of hot 
alcohol and filtered. The filtrate is freed from 
alcohol by vigorously boiling and, when cooled, 
deposits long needles of the base which melt 
at 181°. 

Semiogamazide HjN-CO-CO-NH-NHj (Kerp 
and Unger, Ber. 1897, 30, 586). This substance 
may be prepared by gently heating oxamethane 
with an alcoholic solution of hydrazine for a 
short time on the water bath. It crystallises in 
slender lustrous leafiets which melt and decom- 
pose at 220-221°. Semioxamazones are pro- 
duced in quantitative yield from aldehydes, but 
the ketones react in a less general manner and 
seem to require special conditions for their 
formation. 

Aminoguanidine H,N-C(NH)NH-1IH, is 
prepared from nitroguanidine on reduction 
(Thiele, Annalen, 270, 23; D. R. P. 59241; 
Frdl. iii. 16), and from cyanamide, hydrazine 
hydrochloride and alcohol (Fellizari and Cuneo, 
Gazz. chim. ital. 1894, 24, 453). The hydro- 
chloride forms long prisms from dilute alcohol 
which melt at 163°. 

The base is recommended by Baeyer (Ber. 
1894, 27, 1919) for the preparation of derivatives 
of ketones, the following method being used. 

Aminoguanidine hydrochloride is dissolved 
in a little water containing a trace of hydro- 
chloric acid and is then mixed with the .ketone 
together with sufficient alcohol to effect solution. 
The reaction is finished after warming for a short 
time on the water bath, when water and caustic 
potash solution are added and the base is 
extracted by ether. The oil which remains 
after evaporating the ether is suspended in hot 
water and heated with an aqueous solution of 
picric acid. The picrate separates as a crystal- 
Une precipitate which is recrystallised either 
from dilute or absolute alcohol, according to its 
solubility. J. F. T. 

HTDRAZONES. Substances containing the 
complex ■]>N-NH2 react with those compounds 
which have in their molectile an oxygen atom 
doubly bound to carbon, forming condensation 
products in accordance with the general equation 

>C:0+H,N-N< -> >C:N-N<-fH,0. 
Such condensation products are termed hydra- 
zones. Only the carbonyl compounds which 
belong to the groups of the aldehydes and 



HTDRAZONES. 



67 



ketones react, however, in this manner ; the 
carboxylio aoids containing the group COOH do 
not react as if they contained oarbonyl oxygen, 
but give hydrazides in accordance with the 
scheme ' 

R-COOH+HjN-N<-^ R-CO-NH-N<+HjO. 
One or more carbonyl- groups present in the 
compound may enter into combination with 
the hydrazine residue, forming — for example, in 
the case of the dicarbonyl derivatives — dihydra- 
zones, thus : 

—CO C=N— N< 

—CO C=N— N< 
Those dihydrazones, which are derived from 
dicarbonyl compounds having the two earbonyl- 
groups on contiguous carbon atoms, are termed 
Osazones. Thus in the case of the two com- 
pounds formed from glyoxal CHOCHO and 
phenylhydrazine 
CHO 

{ is glyozalphenylhydrazone ; 

CH:N-NH0,H5 
OHrN-NHCsHs 

I is glyoxalphenylosazone 

CH:N-NH0,Hb 

(Fischer, Ber. 1888, 21, 985). 

Phenylhydrazine CeHj-NH-NHj was the 
first member of the class of the hydrazines to be 
applied to the characterisation and isolation of 
the carbonyl compounds (oomp. E. Fischer, Ber. 
1884, 17, 672), but since that time the reaction 
has been shown to be a general one for all 
derivatives of hydrazine having a primary 
amino group intact. 

Hydrazine HjN'NH, itself reacts with 
aldehydes and ketones, as Curtius has shown, 
forming either hydrazones of the type 

R-CHiN-NHj 
(or RRCiN-NHj), in which one molecule of 
the carbonyl compound reacts, or azines of the 
formula R-CH : N-N : CHR) or 

ERC:N-N-CRR) 
in which two molecules of the carbonyl deriva- 
tive take part. The azines from the aldehydes 
are known as aldazinea, those from the ketones 
as ketazines. In the ajiphatic series, the alde- 
hydes pass directly into the aldazines when 
treated with hydrazine, whilst the hydrazones, 
RRCiN'NHj, which can be isolated from the 
product of the interaction of ketones and 
hydrazine, readily pass into the ketazine and 
hydrazine in accordance with the equation 
2(RjC:N-NHj) -> RjC: N-N-Rj-l-HjN-NHj. 

It is apparent that azine formation in the 
manner described above cannot occur with the 
substituted derivatives of hydrazine of the 
general formulae RNH-NHj and RjN-NHa, 
and it is therefore compounds of this type which 
are of such great importance as reagents for the 
preparation of the hydrazones, osazones, and 
semicarbazones. 

Constitution of the hydrazones. The con- 
stitution of the hydrazones formed from car- 
bonyl compounds by the action of secondary 
asymmetric hydrazines RjN-NHj, admits of 
ordy one formula, namely, RjN-NiCRj; but 
the hydrazones formed from the primary 
hydrazines may conceivably be constituted in 



accordance with one or other of the three forms 



/NH 



>C/: 



H 



(1)>C:N-NHR (2) yO<^^^ (3)>..^N:NR 

Of these, formula (2) may be discarded, 
because the same compound is formed by the 
interaction of benzaldehyde and phenylethyl- 
hydrazine 
C„H5-CH04-H,N-N(CaH,)C,H5 

=0eH5-CH:N-N(CjH5)CiH5 
as by the ethylation, by means of sodium eth- 
oxide and ethyl iodide, of the hydrazone formed 
by the condensation of benzaldehyde and 
phenylhydrazine 
CsHj-CHO H-H jN-NH-CeHj 

=CeH5-CH:N-NH-C5H5 
CeHj-CH; N-NH-OeHj+NaO-CA 

=CsHj-CH : N-NNa-CjH.-f HO-CoH. 
C.Hs-CHiN-NNa-OsH.-fCHsI - 

= C.H5-caa : N-N(C,H5)C,H5-fNaI. 

The azo formula (3) would appear, at first 
sight, to be untenable, because the hydrazone 
prepared from phenylhydrazine and acetalde- 
hyde is different from ethaneazobenzene 

CHj-CHj-NiN-CsHj 
which is prepared by the oxidation of ethane- 
hydrazobenzene. It has been shown, however, 
that there is an intimate connection between 
these two substances, and that the change 

CeHj-N : N-CjHj -^ CeHj-NH-N : CHCH, 
is readily effected by mineral acids (Fischer, 
Annalen, 1879, 199, 328 ; Ber. 1896, 29, 703), 
or by sodium ethoxide (Bamberger, Ber. 1903, 
36, 56) ; whereas the reverse change 
CsHs-NH-N : CHCH. -^ C^Hj-N : N-CHjCH, 
is effected by the action of light (Chattaway, 
Chem. Soo. Trans. 1906, 89, 462). The question 
as to the azo or hydrazone structure of these 
compounds has given rise to a great deal of 
controversy, and is even at the present time 
not definitely settled. The discussion may be 
said to have arisen owing to the discovery made 
by Japp and Klingemaun (Ber. 1887, 20, 3284, 
3398), that the hydrazone of pyruvic acid 

C8HjNH-N:C(CH3)C0i,H 
was identical with benzene-o-azopropionio acid 
CeHjN : N-CH(CH3)C02H. R. Meyer (Ber. 1888, 
21, 118) also showed that the dicarboxylic 
acid obtained by the hydrolysis of the ethyl salt 
which is formed by the interaction of benzeue- 
diazonium chloride and ethyl malonate, thus : 
CeH5-NjCH0Hj(C02R)2 

=C6Hi-N : N-CH(COjR)j+HCl 
CjHs-N : N-CH(COjE)2+2HjO 

=CsH5-N : N-CH(C02H)2+2R-OH 
was identical with the compound prepared by 
the condensation of mesoxalic acid and phenyl- 
hydrazine, thus: 
CeH,-NH-NHa+C0(C0jH)2 

=06H5-NH-N : C(C0aH)2-f H,0. 
That is to say, the question arose as to whether 
these compounds were true hydrazones having 
the structure R'NH'N:C<^ or whether they 
were azo oomjiounds having the structure 
E-N:N-CH<. 

Since that time many other instances of the 
same kind as that recorded by these chemists 
have been investigated, and repeated attempts 
have been made to establish either one or other 



58 



HYDEAZONES. 



of these constitutional formulae for the hydra- 
zones (R. Meyer, Be*. 1891, 24, 1241; Japp 
and Elingemann, Annalen, 1888, 247, 190; 
V. Meyer, Ber. 1888, 21. 11; HaUer, Compt. 
rend. 1888, 106, 1173 ; Beyer and aaisen, Ber. 
1892, 25, 746; v. Peohmann, Ber. 1892, 25, 
3190 ; Bamberger and Wheelwright, ibid. 1892, 
25, 3201 ; Bamberger, ibid. 1894, 27, 2591). 

Much of the evidence falls under the head of 
the constitution of the azo compounds, and the 
article under this heading should be consulted 
for further information ; but it is evident that 
much still remains to be learnt regarding the 
conditions controlling the tendency of a hydro- 
gen atom attached to the terminal atom of any 
system such as 

R^ lv2 Iw XV3 Ki R^ R. 

I I I I I I I 

HN-N:N HC-C:C HC-N:N HCC:0 



1 I 
K^ R4 R2 



R, 



to pass to the other terminal atom with a. 
consequent shifting of the double bond, thus : 
Ri Rf R R^ R^ R^ xvi 

II II II I 

N:N-NH C:CCH C:NNH C:C-OH 

III I 

xvj R^ £V2 Ra 

The evidence at present available seems to 
show that the hydrogen atom in compounds of 
this type may assume either one or other of 
these positions, in which case definite compounds 
are formed, having, as in the case under dis- 
cussion, either the azo 01 hydrazone form : on 
the other hand, there may be tautomerism 
between the two forms, in which case the hydro- 
gen atom acts as if it vibrated between the two 
terminal atoms of the system (c/. Bulow and 
Hopfner, Ber. 1901, 34, 71 ; Bulow and Hailer, 
ibid. 1902, 35, 915). There is, however, little 
doubt that in the majority of cases the com- 
pounds formed from benzenediazonium chloride 
and substances of the type of ethyl malonate as 
well as those produced by the action of phenyl- 
hydrazine on carbonyl compounds have the 
hydrazone structure. 

The formation of phenylhydrazones. As a 
rule, phenylhydrazlne readily reacts with ketones 
and aldehydes, yielding phenylhydrazones, 
which are crystalline and of definite melting- 
point. The following method generally gives the 
phenylhydrazone in a pure condition. Phenyl- 
hydrazine is dissolved in 50 p.c. aqueous acetic 
acid and diluted with three times its volume of 
water. The carbonyl compound diluted when 
necessary by a suitable solvent is then added 
and the whole is warmed. The phenylhydra- 
zone then separates either in the crystalline con- 
dition or as an oil which usually crystallises 
when scratched with a glass rod. 

Derivatives of phenylhydrazlne, such as 
phenylhydrazine-p-sulphonic acid 
CjH4(S03H)NH-NH2. 
p-nitrophenylhydrazme C,Hj(NO,)NH-NHj 
or p-bromophenylhydrazine 

CeH«(Br)NH-NH„ 
may be used for the production of hydrazones ; 
moreover other hydrazines, such as /3-naphthyl- 
hydrazine C,oH,-NH-NH„ methylphenyl- 
hydrazine C,H^(CH,)N-NH|, a«^m-diphenyl- 
hydrazine (CfgH^)3N-KH2, and benzylphenyl- 



hydrazine CsH5-C!H,(C,H5)N-NHj are often 
used for this purpose {cp. Hydrazines). 

Reaction of the hydrazones. When warmed 
with mineral acids, the hydrazones are more or 
less readily hydrolysed into the carbonyl com- 
pound and the hydrazine. This reaction pro- 
ceeds, however, inuch more readily when the 
hydrazone is warmed with an aqueous solution 
of pyruvic acid, when the following reaction 
often occurs (Fischer and Aoh, Annalen, 1889, 
253, 57) :— 
R.C : N-NH-C,H.+CH,CO-COsH 

=RjC0+CH3C( :N-NH0,H5)C0jH. 

The hydrazones of the aliphatic aldehydes 
and ketones form addition products with hydro- 
cyanic acid, yielding nitriles in accordance with 
the equation 
aHj-NH-NiCRj-fHCN 

=C.Hb-NH-NH-C(CN)-Rj 
(cp. V. Miller and Ploohl, Ber. 1892, 25, 2023). 

Hydrazones when reduced break at the 
point of union of the two nitrogen atoms and 
pass into amines. This method has been made 
use of by Tafel (Ber. 1886, 19, 1924 ; 1889. 22, 
1 854) for the formation of primary amines from 
aldehydes and ketones. Thus the hydrazone 
of acetaldehyde yields in this manner a mixture 
of aniline and ethylamine 
CH,-OH : N-NH-C,H5+4H 

=CH,-CH2NHj+C,H5NH2. 
When oxidised by amyl nitrite, hydrazones are 
converted into hydrotetrazines (V. Pechmann, 
Ber. 1893, 26, 1045). 

CeHj-CH : N CeHs-CH : N N : CHCjHs 

2 I -» M 

CeH,-NH C„H5NN-C,H, 

These compounds dissolve in concentrated 
sulphuric acid, forming intensely coloured 
solutions. It is probable that Bulow's reaction 
for hydrazides and hydrazones, which depends 
on the formation of a coloured solution, when 
the hydrazone, dissolved in concentrated sul- 
phuric acid, is treated with a drop of ferric 
chloride solution, is due to the production of the 
hydrotetrazine. 

The action of zinc chloride on hydrazones 
causes the elimination of ammonia and leads to 
the formation of derivatives of indole (E. 
Fischer and Hess, Ber. 1884, 17, 559; E. 
Fischer, ibid. 1886, 19, 1563; Annalen, 1886, 
236, 116 ; Brunner, Monatsh. 1895, 16, 183, 849). 

The reaction may be expressed by the 
following general equation but is difficult to 
follow by means of structural formulae : — 



CeHj-NH-N:C 



CH. 



\ 



H, 



CH 

y \ 

CeH. 0-CH, 



This reaction has been made use of by Ewins 
(Chem. Soc. Trans. 1911, 99, 270) for the 
preparation of 3-3-aminoethylindole, thus — 
C.Hb-NHNHj+CHj-CHj-CHj-NH, 



CCH,-CH,-NH, 

/\ 
=C,H4 CH 



CH(00,H.). 

+NH,+2CaH,0H. 



HYDROGEN. 



This compound was found to be identical 
with the base obtained by the action of putre- 
factive bacteria on tryptophan. It will be 
noticed that, owing to the unstable character of 
the aldehyde, it could not be used in the free 
state for the production of the hydrazone and 
that the acetal derivative was used in its place. 
Hydrazones which are formed from ;3-ketonic 
ethyl salts pass, when heated, into alcohol and a 
derivative of pyrazolone. Thus the phenyl- 
hydrazone of ethyl acetoacetate, which is a 
colourless crystalline substance and is therefore 
probably ethyl benzenehydrazoorotonate formed 
in accordance with the equation 
C2HgC02'CH2 

I +H2N-NH-C.Hs 
CH,-CO 

CaHjCOa-CHj 

-> I 

CH3-C(0H)NH-NH-0eHj 
CjHj-COj-CH 

-> II 

CHs-C-NH-NH-CjHj 

passes when heated at 200° under diminished 
pressure into phenylmethylpyrazoloue 



-OH 



CjHsOj-^CO-CH QQ 

cyi;3;Hi II ->c.H,-N< ' \\ 

XnhJ-CH, , ^NH-C-CH, 

In many cases the formation of the pyrazo- 
lone derivative takes place immediately without, 
the intermediate formation of the hydrazone. 

Stereoisomerism, in accordance with the 
Hantzsch- Werner hypothesis, has been observed 
among the hydrazones, and in certain instances 
the two forms 

R— C— H R— C— H 

II and - II 

N— NHR RHN— N 

have been isolated {ep. E. Fischer, Ber. 1884, 
17, 675 ; Biltz, ibid. 1894, 2288 ; Hantzsch and 
Hornbostel, ibid. 1897, 30, 3003; Bamberger 
and Schmidt, ibid. 1901, 34, 2001). 

As already mentioned, the name ' osazone ' 
denotes a compound containing in its molecule 
two hydrazine residues, R — NH — ^N=, attached 
to two contiguous carbon atoms. E. Fischer 
(Ber. 1884, 17, 679) obtained fromcarbohydrates 
a series of characteristic compounds formed by 
the introduction of two phenylhydrazone groups 
into the molecule of a carbohydrate. The com- 
pound from dextrose was termed 'phenyl- 
glucosazone ' ; that from galactose ' phenyl- 
galactosazone,' and so on. Later, when it was 
found that in these compounds the two phenyl- 
hydrazine residues were in contiguous positions, 
the name ' osazone ' was applied to all com- 
pounds containing this particular grouping 
(E. Fischer, Ber. 1888, 21, 986). Osazones are 
formed by the action of two molecules of phenyl- 
hydrazine on o-dicarbonyl compounds, namely, 
such as contain the group CO 'CO ; 
CH.CO 

I +2C,H6NH-NH, 
CH,-CO 
Dlacetsrl, 



OH,— C:N-NH-C,H, 

Biacetylphenylosazone, 



+2HaO 



The yellow colouring matters known as 
' tartrazines ' are derived from osazones, formed 
in this way from dihydroxytartaric acid. 

Osazones are also formed by the action of 
phenylhydrazine on compounds containing the 
group — CH(OH)-CO — , thus on a-keto-aloohols 
and «-aldehydo-alcohols ; and it is the members 
of the carbohydrate family belonging to these 
classes which yield osazones. In the cold, 
unless on long standing, oiJy the carbonyl 
group reacts with phenylhydrazine, and a 
hydrazone containing the group 

-CH(0H)C(N2H-C,HJ— 
is formed ; but this compound, on heating with 
excess of phenylhydrazine, is converted into an 
osazone, the alcohol, group also taking part in 
the reaction. The moleciUe of hydrogen which 
is removed in this process reduces a molecule of 
phenylhydrazine to aniline and ammonia. 
Thus with dextrose — 
0Hj0HrCH0H],CH0 -f SC^HsNH-NHj 
^CHjOH[CHOH],C(NjH-06H5)CH(N,HCbH5) 
Phenylglucosazone. 

-fNHAHs+NHj+^H^O. 

These osazones have proved of great use in 
identifying various sugars. Sometimes, how- 
ever, two distinct sugars yield the same osazone : 
thus . laevulose, like dextrose, gives phenyl- 
glucosazone : — 
CH20H[CHOH],CO-CH20H+3CeHjNH-NH, 

LcGvuloae. 
-^CHjOH[CHOH]3C(NjHCsH5)CH(NjHC6H5) 
Fhenylglucosazone. 
+NH2C.H,)+NH3+2H20 
the o-aldehyde alcohol and the o-keto alcohol- 
yielding the same osazone. 

The osazones are crystalline compounds, of 
a yellow colour, and generally have a definite 
melting point, by means of which they may be 
identified. Concentrated sulphuric acid dis- 
solves the various osazones, giving characteristic 
colourations, and the solution generally exhibits 
some particular colour change on standing 
(Japp and Klingemann, Ber. 1888, 21, 549). 
Fuming hydrochloric acid hydrolyses the osa- 
zones in the cold into phenvlhydrazine and the 
a-dioarbonyl compound from which they are 
derived (E. Fischer, ibid. 1888, 21, 2631). 

J. F. T. 

HYDRAZONE COLOURING MATTERS v. 
Pyrazolone coloueeno mattbbs. 

HYDRINDENE v. Ketones and Indbnb, 

HYDRINDONE v. Indene. 

HYDRIODIC ACID v. Iodine. 

HYDROBROMIC ACID v. Beominb: 

HYDROCARBOSTYRIL v. QuiNOLDtB. 

HYDROCHLORIC ACID v. Chlokine. 

HYDROCURCUMIN v. TiraMEKic. 

HYDROCYANIC ACID v. Cyanides. 

HYDROFLUORIC ACID v. Ft-uoEatE. 

HYDROFLUOSILICIC ACID u. yFLUOEiNE. 

HYDROGELS t>. CoiiOiDS. 

HYDROGEN. At.wt. 1008. Symbol H. 
The existence of this gas was recognised in 
the 16th century; its combustible property 
was discovered in the following century by 
Turquet de Mayerne, and in 1700 Lemery 
observed the detonating property of a mixture 
of air and hydrogen. 

Cavendish, in 1766, showed that when the 
gas was produced from dilute acid and one ol 



60 



HYDROGEN. 



the metals, iron, zinc, oi tin, it was obtained in 
amount varying with the metal used. 

Hydrogen was for a time confounded with 
other combustible gases, such as maish-gas, 
carbon monozide, and vapour of ether ; all were 
supposed to contain the same inflammable 
principle, phlogiston, modified by variable 
amounts of other substances. 

Macqner and De la Metherie first observed, 
in 1766, that water was produced by burning 
hydrogen, but it was then thought that other 
products than water were produced at the 
same time, and Lavoisier made many experi- 
ments with the object of detecting the presence 
of an acid which he imagined should be among 
the products of combustion, as was the case in 
the combustion of such bodies as sulphur, 
carbon, phosphorus, &c. Cavendish, however, 
in 1781, proved conclusively that water was 
the only product of combustion when hy- 
drogen burns in ail or oxygen, and that if a 
mixture of hydrogen and oxygen in the pro- 
portion of two volumes of the former to one of 
the latter were burnt, the whole of the gases 
were converted into water. 

Sources. Hydrogen occurs free in nature in 
the gaseous mixtures evolved from certain 
volcanos (Bunsen, Ann. Chim. Phys. 1853, [iii.] 
38, 215; Deville, Compt. rend. 1862, 55, 78). 
The gases evolved from Mte. Eelee in Marti- 
nique during the eruptions of 1902 contained 
22-3 p.c. of hydrogen by volume (Moissan, 
Compt. rend. 1902, 135, 1085). It also occurs 
in the jets of steam, known as fumerolles, which 
occur in Tuscany and other places. The gases 
issuing from the salt beds of Stassfurt (Bei- 
chardt. Arch. Pharm. 1860, [ii.] 103, 347; 
Precht, Ber. 1880, 13, 2326), and Wieliczka 
(Rose, Pogg. Ann. 48, 353) contain hydrogen, 
and it also occurs in the gases given off by the 
oil-wells of Pennsylvania (Engler, Ber. 1888, 21, 
1816). Hydrogen has been found occluded in 
certain meteorites (Graham, Proo. Roy. Soc. 
1867, 15, 502 ; Mallet, ibid. 1872, 20, 365), and 
in a large number of minerals (Ramsay and 
Travers, Proc. Roy. Soc. 1897, 60, 442 ; Tilden, 
ibid. 1897, 60, 453). To a very slight extent, 
hydrogen occurs free in the atmosphere (Gautier, 
Ann. Chim. Phys. 1901, [vii.] 22, 5 ; Liveing and 
Dewar, ibid. 1901, 22, 482 ; Rayleigh, Pha Mag. 
1902, [vi.] 3, 416 ; Leduo, Compt. rend. 1902, 135, 
860, 1332). According to Claude (Compt. rend. 
1909, 148, 1454), there is less than 1 part of 
hydrogen in one million parts of air. Hydro- 
gen is also produced in the decay of various 
organic bodies, being found in the intestinal 
gases of many animals (Tappeiner, Ber. 1881, 
14, 2375). 

Spectroscopic observations have shown that 
hydrogen completely surrounds the sun, forming 
an envelope which has received the name of the 
chromosphere. Hydrogen also occurs in certain 
stars and nebulae. 

In a state of combination, hydrogen forms 
one-ninth the weight of water and one-fourth 
the weight of marsh-gas. It also occurs in 
smaller quantities in combination with phos- 
phorus, sulphur, iodine, bromine, carbon, and 
nitrogen. It is an essential constituent of all 
acids ; most animal and vegetable substances 
contain it, and it is a constituent of many 
minerals. It exists in the air in small quantities 



in combination with nitrogen as ammonia ; and 
in certain mineral and volcanic springs it is 
found in combination with sulphur and chlorine 
as sulphuretted hydrogen and hydrochloric acid 
respectively. 

Preparation. (I) Electrolysis of certain 
aqueous solutions. — Pure hydrogen is readily 

frepared by the electrolysis of a mixture of 
part of sulphuric acid and 10 parts of water, 
between platinum electrodes. The potential 
difference between the terminals must exceed 
1-7 volts. The hydrogen is evolved at the 
cathode, and suitable provision must be made 
to prevent oxygen from the anode diffusing into 
the hydrogen. A convenient method consists 
in immersing the anode in a mass of liquid 
zinc-amalgam, which absorbs the oxygen com- 
pletely, forming zinc oxide and eventu^y zino 
sulphate. The current from three or four 
Bunsen elements is sufficient to work such an 
electrolytic cell for laboratory use. A suitable 
piece of apparatus is described in Amer. Chem. J. 
1897, 19, 810. A 30 p.c. solution of sodium 
hydroxide may also be employed ; plate nickel 
electrodes are most convenient, and a useful 
piece of apparatus for this purpose is described 
by V^zes and Labatut (Zeitsch. anorg. Chem. 
1902, 32, 464). Hydrogen prepared from 
sodium hydroxide solution always contains a 
little organic matter, owing to the presence of 
carbonate in solution (Morley) ; it can be ob- 
.tained quite pure by electrolysing a solution of 
pure recrystallised baryta (Baker, Chem. Soc. 
Trans. 1902, 81, 400). 

These electrolytic methods are employed on 
a commercial scale, dilute sulphuric acid being 
electrolysed between lead electrodes, or sodium 
hydroxide between iron electrodes. The chief 
difficulty encountered is that of preventing 
diffusion between the hydrogen and the oxygen 
simultaneously produced. The introduction of 
diaphragms increases the resistance of the cell, 
and is therefore to be avoided if possible. 
Various patterns of cell have been devised, and 
are described in J. Soc. Chem. Ind. 1900, 19, 
1120 ; 1901, 20, 258 ; Eng. Pats. 2820, 1902, and 
27249, 1903; Fr. Pats. 355652, 1905, and 397319, 
1908 ; D. R. P. 198626, 1906. 

(2) Chemical decomposition of water. — Hydro- 
gen may be prepared by decomposing water ; a 
large number of readily oxidisable substances 
can be emjdoyed for this purpose. 

The alkaU metals and the metals of the 
alkaline earths decompose water at ordinary 
temperatures, liberating hydrogen and pro- 
ducing the corresponding metallic hydroxide. 
The action is very violent, particularly with 
potassium, rubidium, and caesium. The re- 
actions can be readily controlled, however, by 
employing the amalgams of these metals. The 
action of steam on pure sodium has been used 
for the preparation of pure hydrogen (Scott, 
Phil. Trans. 1893, 184, 648 ; MeUor and RusseU. 
Chem. Soc. Trans. 1902, 81, 1279), and the use 
of sodium, mixed with oil, aluminium, and in- 
fusorial earth, for the preparation of hydrogen 
on a commercial scale has been patented 
(U.S. PafB. 883531, 1908; 909536, 1909). 

Magnesium decomposes water at tempera- 
tnres above 70' (Ditto, Compt. rend. 1871, 73, 
108), and bums vigorously when heated in 
steam. Magnesium amalgam decomposes cold 



HYDROGEN. 



61 



watei (Eleck and Basset, J. Amer. Chem. Soc. 
1896, 17, 789). 

Aluminium does not decompose watei unless 
some means is afiorded of removing the oxide 
from the surface of the metal. Tms is easily 
effected by amalgamating it with ,'5 its weight 
of mercury, when the amalgam produced readily 
decomposes water and can be employed as a 
source of pure hydrogen (Bailie and Fery, Ann. 
Chim. Phys. 1889, [vi.] 17, 246; Wislicenus 
andKaufEmann.Ber. 1895, 28, 1323). Hydrogen 
is readily obtained pure by slowly adding water 
to a mixture of fine aluminium filings containing 
1 to 2 p.c. of mercuric chloride and 0'5 p.c. of 
potassium cyanide, keeping the temperature at 
70° (Mauricheau-Beaupre, Compt. rend. 1908, 
147, 310 ; Fr. Pat. 392725, 1908). One kilo, of 
this mixture yields 1300 litres of hydrogen. 

At a red heat, water vapour is easily decom- 
posed by iron, hydrogen and triferric tetroxide 
being produced (Lavoisier, CBuvres, 2, 360). 
This method is employed on a large scale and 
has been the subject of numerous patents (Eng. 
Pats. 7518, 1887; 20752, 1890; 4134, 1891; 
28721, 1896; 10356, 1903; 21479, 1908; Fr. 
Pats. 373271. 1907; 386991, 1908; 395132, 
1908 ; U.S. ■ Pat. 971206, 1908 ; D. B. P. 
226453, 1909). The oxide produced is reduced 
to metal by heating with coal OB by some other 
process, and used again. 

Steam is readily decomposed by passing it 
over red-hot coke, when a mixture coijsisting 
essentially of carbon monoxide and hydrogen 
in approximately eqaal volumes, is produced, 
known as water-gas [v. Gas, wateb). Numerous 
methods have been proposed for the purpose.of 
preparing hydrogen commercieilly from this 
mixture. In one process (Frank, Fr. Pat. 
371814, 1906), the dried mixture is passed 
over calcium carbide at a temperature above 
300°; carbon monoxide and dioxide are 
removed as calcium oxide, calcium carbonate, 
and carbon, while the nitrogen present is 
converted into calcium cyanamide. The oxides 
of carbon may be partially removed by a 
preliminary cooling process, whereby the mon- 
oxide is liquefied and the dioxide solidified. 
Jouve and Gautier (Fr. Pat. 372045, 1906) pro- 
pose to pass the gas through a porous partition 
in order to separate the hydrogen by reason of 
its rapid power of diffusion. It is said that by 
one such operation the percentage of carbon 
monoxide may be reduced from 45 to 8 p.c. In 
other processes, the carbon monoxide is removed 
by chemical means ; for this purpose it is de- 
composed by heating to bright redness with 
excess of steam, when the monoxide is replaced 
by an equal volume of hydrogen, carbon dioxide 
being produced, which may be removed by 
solution in water 01 by absorbing it in mUk of 
lime (Henry and Hembert, Compt. rend. 1885, 
101, 797 ; D. B. P. 224862, 1907). 

The oxidation of carbon monoxide by steam 
with the liberation of hydrogen can be effected 
at 400°-600° in the presence of reduced iron or 
nickel (Fr. Pats. 355324, 1905; 375164, 1906; 
cf. Mond and Langer, Eng. Pat. 12608, 1888, and 
Fr. Pat. 361429, 1905). 

Hydrogen free from compounds of carbon 
and oxygen, can be prepared by heating coke, 
impregnated with 10 p.c. potassium carbonate 
and mixed with five times its weight of burnt 



lime, in a current of steam at 660°-750° (J^ng. 
Pat. 8734, 1910). 

The decomposition of steam may also be 
effected by passing it over red-hot barium sul- 
phide, which becomes oxidised to sulphate, with 
the simultaneous formation of hydrogen (Fr. 
Pat. 361866, 1905). The sulphate is reduced 
with coal 01 producer gas to sulphide, and used 
again. 

(3) Action of meiaU on acids. — The common- 
est method of preparing hydrogen for laboratory 
purposes consists in acting upon granulated zinc 
with either dilute hydrochloric acid (1 of acid to 
2 of water), or sulphuric acid (1 of acid to 8 of 
water), when hydrogen is evolved and zinc 
chloride or sulphate left in solution. Very pure 
hydrogen is obtained from pure zinc and pure 
diluted acid, but the action is extremely slow. 
A regular stream of the- gas may be obtained, 
however, by adding a little platinio chloride 
solution. Platinum is deposited over the 
surface of the zinc, and the liberated hydrogen 
escapes freely from the surface of the platinum, 
leaving the zinc surface free from bubbles of 
gas (Gourdon, Compt. rend. 1873, 76, 1250). 
A similar effect is produced by adding a small 
quantity of a salt of copper, silver, gold, tin, 
antimony, bismuth, nickel, or cobalt. 

Other metals, e.g. aluminium, magnesium, 
and iron, may be used instead of zinc for 
generating hydrogen from acids. Pure hydro- 
gen is readily prepared by acting upon alumin- 
ium with mercuric chloride solution slightly 
acidified with hydrochloric acid (Bodenstein, 
Zeitsch. physikal. Chem. 1897, 22, 3). The use 
of zinc, and more particularly of iron and sul- 
phuric acid upon a commercial scale is very 
common (v. Eng. Pats. 15509, 1897; 16277, 
1896 ; 17615, 1898 ; 25084, 1897). 

(4) Action of metals and non-metals on 
aXkalis. — The metals, zinc, aluminium, and tin, 
readily dissolve in warm concentrated alkali 
hydroxide solutions, liberating hydrogen and 
forming alkali zincate, aluminate, and stannate 
respectively. Very pure hydrogen is thus pro- 
duced from aluminium free from carbon. The 
non-metaUic element, silicon, similarly dissolves, 
and considerable quantities of hydrogen are now 
prepared by heating powdered E^con with 
sodium hydroxide solution and milk of lime 
(D. R. P. 216768, 1908 ; Bug. Pat. 21032, 1909) 
\v. infra. Hydrogen for Balloons). 

Hydrogen may be prepared by heating 
slaked lime with either zinc dust (Schwarz, Ber. 
1886, 19, 1141) or coaL The resulting calcium 
carbonate in the latter process may be recon- 
verted into slaked lime by heating in steam 
(Bloxam). 

(5) Decomposition of metallic hydrides. — ^The 
hydrides of the alkali metals and those of the 
alkaline earths readily decompose water at 
ordinary temperatures, liberating hydrogen and 
forming the corresponding metallio hydroxide. 
The use of calcium hydride for preparing hydro- 
gen is very convenient, since the hydride is 
readily portable, and each gram of the substance 
yields more than 1 litre of hydrogen when de- 
composed by water. The hydrogen liberated 
is twice that which is absorbed by the metallic 
calcium in the preparation of the hydride (Fr. 
Pat. 327878, 1902); (v. infra, Hydrogen for 
Balloons). 



62 



HYDROGEN. 



Palladium foil is capable of directly ab- 
sorbing large quantities of hydrogen ; from the 
substance thus produced, pure hydrogen is 
readily obtained by heating it under reduced 
pressure (o. inpa, p. 65). 

Purificaiion. — ^The electrolysis of either dilute 
sulphuric acid or a solution of pure baryta, 
yields practically pure hydrogen, as also does 
the action of steam on pure sodium. Most 
methods of preparation, however, yield hydro- 
gen containing more or less of a number of 
impurities, nearly all of which may be removed 
by treating the gas with reagents capable of 
absorbing them. The precise nature of most of 
the impurities depen(& upon the method of 
preparation employed, but one in particular, 
viz. atmospheric air, is common to nearly all 
methods. Its presence in the gas is due partly 
to its presence in the liquids emj^oyed in the 
preparation of the gas, a source of error which 
may be diminished by previously boiling the 
solution, partly to the difficulty of completely 
expelling air from the apparatus, and partly 
owing to leakage into the apparatus tnrough 
cork or rubber joints, which should therefore be 
reduced to a minimum. The oxygen thus 
introduced may be removed by passing the gas 
over red-hot coppes or spongy platinum or 
through chromous chloride solution, but the 
nitrogen cannot be similarly removed. 

A convenient but expensive method of 
obtaining pure hydrogen consists in passing 
the dried, approximately pure gas over 
palladium, the metal having been previously 
strongly heated, introduced into a tube fitted 
with a stopcock and the tube evacuated. The 
metal is allowed to cool during the absorption of 
the gas. The gas left in the apparatus is finally 
pumped out. !From the palladium-hydrogen, 
pure hydrogen is readily obtained by attacfing 
the palladium tube to the apparatus into which 
the gas is to be introduced, and gently warming 
the metal. 

Hydrogen prepared from acid and ordinary 
iron, which contains a certain amount of carbide, 
invariably contains gaseous hydrocarbons which 
give the gas a most unpleasant odour, and this 
method of preparation is never used for labora- 
tory purposes. The hydrocarbons may be re- 
moved by passing the gas through alcohol, or a 
tube filled with pieces of wood-charcoal or 
paraffin (Stenhouse, Annalen, 1858, 106, 125 ; 
Varenne and Hfebre, BuU. Soc. chim. 1877, [ii.] 
28, 523). 

According to Morley, the purest redistilled 
zinc always contains a little occluded oxides of 
carbon, which find their way into hydrogen 
prepared from the metal and acid. The- com- 
mercial metal may also contain, besides a little 
'lead, traces of sulphur, arsenic, antimony, 
carbon, silicon, and even phosphorus, which 
cause the hydrogen generated from the metal by 
means of acid to contain the corresponding 
gaseous hydrides. Sulphuric acid may contain 
sulphur dioxide, which will be partly evolved 
with the hydrogen and partly reduced to hydro- 
gen sulphide (Kolbe, .Mnalen, 1861, 119, 174), 
and also nitrogen compounds, which lead to the 
formation of nitrogen and nitrous oxide in the 
hydrogen. Frequraitly sulphuric acid contains 
arsenic and selenium, which lead to the formation 
of the corresponding hydrides. Hydrochloric 



acid prepared from sulphuric acid may contain 
the same impurities. 

Sulphur dioxide, the hydrides of sulphur, 
selenium, silicon, and hydrogen chloride carried 
over by the hydrogen may be absorbed in a 
solution of potassium hydroxide. The hydrides 
of phosphorus, arsenic, and antimony may be 
absorbed by solutions of various metallic salts, 
e.g. mercuric chloride, lead nitrate, or silver 
sulphate (Dumas, Ann. Chim. Phys. 1843, [iiL] 
8, 189). 

All the above impurities are decomposed 
when the hydrogen is passed over red-hot copper 
turnings. The small quantity of nitrogen that 
may be introduced by the decomposition of 
oxides of nitrogen is usually not inconvenient. 

For laboratory purposes, hydrogen is best 
purified from phosphine, arsiue, and stibine, 
by passing it through saturated permanganate 
solution and then through 5-10 p.c. silver 
nitrate. After washing hydrogen with concen- 
trated permanganate solution, however, the gas 
contains traces of oxygen. For removing traces 
of arsine from large quantities of hydrogen, 
bromine is the best absorbent ; on a technical 
scale potassium hypochlorite or bleaching 
powder may be substituted (Keckleben and 
Lockemann, Zeitsch. angew. Chem. 1908, 21, 
433). 

Arsine is said to be completely removed 
from hydrogen by bubbling the gas through 
petroleum spirit cooled by liquid air to —110°, 
and the process has been recommended for 
technical use (Compt. rend. 1903, 136, 1317). 

An elaborate method for puriJEying hydrogen 
by freezing out the impurities is described by 
Kamerlingh Onnes (Proc. K. Akad. Wetensch. 
Amsterdam, 1909, 11, 883) ;' using 25 litres of 
liquid air, 10,000 litres of hydrogen can be 
purified in 8 hours. 

Hydrogen may be dried for ordinary purposes 
by passing it over anhydrous calcium chloride 
or through concentrated sulphuric acid. The 
latter process, however, slightly contaminates 
the gas with sulphur dioxide (Dittmar and 
Henderson, Proc. Roy. Soc. Glasgow, 1891, 22, 
33; Berthelot, Compt. rend. 1897, 125, 743; 
MUbauer, Zeitsch. physikal. Chem. 1907, 57, 
649). The use of phosphoric anhydride, free 
from lower oxides, is to be preferred. 

Properties. — Hydrogen is a colourless, odour- 
less, tasteless gas. It is the lightest gas known, 
1 litre of hydrogen at N.T.P. and at sea-level in 
lat. 45°, weighing 089873 ±0-0000027 grams 
(Morley, Zeitsch. physikal. Chem. 1896, 20, 242 ; 
c/. Regnault, Relation des Exper. 2, 121-; Leduc, 
Compt. rend. 1891, 113, 186 ; Thomson, Zeitsch. 
anorg. Chem. 1896, 12, 1). The density of 
hydrogen compared with air is therefore 0-0694. 
The coefficient of expansion at constant pressure 
is 0-003661 (Regnault), and at constant volume 
the pressure coefficient is 0-0036624 (Chappuis). 
The thermal conductivity of hydrogen is seven 
times that of air (Stefan). Between 0° and 200° 
the molecular specific heat at constant pressure 
is 6-81 and at constant volume is 4-81 calories. 
The specific heat increases with rise of tempera- 
ture. According to Mallard and le Chatelier 
(Compt. rend. 1887, 104, 1780), the mean mole- 
cular specific heat of hydrogen at constant 
pressure between 0° and t° is 6-5+0-0006 
(t+273); the value at constant volume is 



HYDROGEN. 



63 



4-700+00004St (Pier, Zeitaoh. Elektreohem. 
1909, 18, 636). The ratio of the speoifio heats 
ia 1-405 (Rontgen). Hydrogen is diamagnetio. 

Hydrogen is very slightly soluble in water, 
its absorption-coefficient between 0° and 25° 
being given by the formula 

0-021528-0-00019216t+0000001728t' 
(Timofejeff, Zeitsch. physikal. Chem. 1890, 6, 
141 ; cf. WinHer, Ber. 1891, 24, 89 ; Bohr and 
Book, Wied. Ann. 1891, 44, 316; Geffken, 
Zeitsch. physikal. Chem. 1904, 49, 257). For 
its solubiUty in alcohol, v. Timofejefl. I.e., and in 
various aqueous salt solutions, v. GefEken, I.e. 

The liquefaction of hydrogen for many years 
presented the most difficult problem to experi- 
menters on the liquefaction of gases. In 1877, 
CaUletet submitted hydrogen to the same pro- 
cess as he had successfully used in the lique- 
faction of oxygen and nitrogen, and observed 
the formation of a fine mist when hydrogen was 
subjected tb a pressure of 280 atmos. and then 
suddenly released. In 1884 Wroblewski (Compt. 
rend. 1884, 100, 979) liquefied hydrogen by 
cooling the gas, under a pressure of 190 atmos., 
by means of boiling nitrogen, and then quickly 
releasing the pressure. By a similar method, 
Olszewski (Compt. rend. 1884, 99, 133 ; 1886, 
101, 238) succeeded in obtaining colourless drops 
of liquid hydrogen. Dewar (Chem. Soc. Proo. 
1895, 229 ; Chem. Soc. Trans. 1898, 528 ; Proc. 
Roy. Soc. 1901, 68, 360) was the first to succeed 
in preparing liquid hydrogen in sufficient 
quantity to show a definite meniscus by applying 
the regenerative process to the compressed gas 
after first cooling it to —205°. Travers (Phil. 
Mag. 1901, [vi.] 1, 411), Olszewski (Ann. Chim. 
Phys. 1903, [vii.] 29, 289), and Nernst and 
Pollitzer (Zeitsch. Elektroohem. 1911, 17, 735) 
have since described processes whereby liquid 
hydrogen may be prepared in quantity. 

Liquid hydrogen forms a clear, colourless 
liquid, boiling at — 252*5° (Dewar, Proo. Roy. 
Soc. 1898, 63, 266 ; Travers, Phil. Mag. 1902, 
[vi.] 3, 535). The vapour pressures of the liquid 
at various temperatures have been measured by 
Travers and Jacquerod (Zeitsch. physikal. Chem. 
1904, 46, 447). At its boUing point the density 
of the liquid is only 0-07. Liquid hydrogen has 
the greatest specific heat of any liquid, namely 
6-4 (Dewar). When cooled by rapid evapora- 
tion under diminished pressure, the liquid 
solidifies to a transparent solid, melting at 
—257° (Dewar) or —258-9° (Travers, Proc. Roy. 
Soc. 1902, 70, 484), and having a sp.gr. at 
-259-9° of 0-0763 (ihid. 1904, 73, 251). The 
critical pressure of hydrogen is 15 atmos. and its 
critical temperature is —243° to .-241° (Dewar). 

The spectrum of hydrogen consists essentially 
of four bright lines — one in the red, corre- 
sponding with Eraunhof er's dark line c, and one 
in the greenish-blue, coincident with the dark 
line p. Their wave-lengths are (Angstrom) 
0=6562, r=4861, blue = 4340, indigo^4101 
in ten-millionths of a millimetre. 

Hydrogen is an inflammable gas, burning in 
air or oxygen with an extremely hot, almost 
colourless flame, and producing water. Even 
with pure hydrogen, however, the centre of the 
flame is coloured green, while the external 
portions are of a violet-blue colour. On re- 
ducing the pressure, the blue colour is trans- 
formed to green, and from that successively to 



yellow, orange, and red. Under increased 
pressure, hydrogen burns with a luminous 
flame. 

The combination of hydrogen. and oxygen 
proceeds slowly at ordinary temperatures in the 
presence of sunlight (Baker, Chem. Soc. Trans. 
1902, 81, 400). The rate of combination is slow 
at 180° (Gautier and Helier, Bull. Soc. chim. 
1896, [iii.] 15, 468), but with rise of temperature 
it becomes quicker and quicker, and explosion 
occurs at about 550° (Gautier and H^ier, I.e. ; 
Berthelot, Compt. rend. 1897, 126, 271 ; Ann. 
Chim, Phys. 1898, [vii.] 13, 30; Meyer and Raum, 
Ber. 1895, 28, 204 ; Bone and Wheeler, Phil. 
Trans. 1906, A, 206, 1 ; Rowe, Zeitsch. physikal. 
Chem. 1907, 59, 41). Mixtures of the two gases, 
if perfectly pure and dry, may be heated to the 
melting-point of silver without combination 
occurring (Baker, I.e.). The ignition-points 
of "various mixtures of oxygen and hydrogen, 
from 3Hj-|-0, to Hj-f 40^, vary between 557° 
and 507° when fired by aofiabatic compression, 
electrolytic gas having an ignition-point of 536° 
(Dixon, Chem. Soc. Trans. 1910, 97, 661 ; c/. 
Fait, J. Amer. Chem. Soc. 1906, 28, 1517 ; 1907, 
29, 1536). The union of hydrogen and oxygen, 
proceeds quickly at ordinary temperatures in 
the presence of finely divided palladium, plati- 
num, iridium, osmium, or gold. 

Hydrogen unites at 250° with sulphur and 
selenium, and at 400° with tellurium. It can be 
made to unite directly with nitrogen under the 
influence of the silent discharge (Chabrier, 
Compt. rend. 1872, 76, 489; Donkin, Proc. 
Roy. Soc. 1881, 31, 281) or of electric sparks 
(Berthelot, Ann. Chim. Phys. 1880, [v.] 21, 386) ; 
compounds of hydrogen with arsenic, phos- 
phorus, antimony, boron, and silicon, can be 
prepared indirectly. 

Hydrogen unites with pure carbon directly 
when heated to 1150°, methane being produced 
(Bone and Jordan, Chem. Soc. Trans. 1897, 71, 
41 ; Bone and Coward, 1908, 93, 1975 ; 1910, 
97, 1219). By passing an electric arc between, 
carbon poles in an atmosphere of hydrogen, 
acetylene is produced, accompanied by a little 
methane and ethane (Berthelot, Compt. rend. 
1862, 54, 640; Bone and Jordan, Chem. Soc. 
Trans. 1901, 79, 1062). 

Gaseous hydrogen combines with fluorine 
even in the dark and at ordinary temperatures, 
with explosive violence, hydrofluoric acid being 
produced (Moissan, Ann. Chim. Phys. 1891, [vi.] 
24, 224). With liquid fluorine at —210°, 
explosion also occurs, and a similar result follows 
on mixing solid fluorine and liquid hydrogen 
(Moissan and Dewar, BuU. Soc. chim. 1897, [iii.] 
17, 932 ; Compt. rend. 1903, 136, 641). 

Chlorine does not combine appreciably with 
hydrogen at ordinary temperatures in the dark, 
but only when heated above 400° or exposed*to 
light. In diffused light,^ combination occurs 
slowly, and there is usually an initial feriod oj 
induction (Bunsen and Roscoe, Phil. Trans.. 
1857, ii. 378) during which the rate of combina- 
tion slowly increases to its maximum value 
and afterwards remains constant. This period 
of induction is due to the presence of traces of 
volatile impurities (Burgess and Chapman, 
Chem. Soc. Trans. 1906, 89, 1399). Under the 
direct action of actinic rays, mixtures of hydro- 
gen and chlorine explode. 



64 



HTDROGEN. 



Hydrogen combines directly with bromine 
above 400°, and slowlj^ even at 100° in the pre- 
sence of light (Eastle and Beatty, Amer. Chem. 
J. 1898, 20, 159). With iodine, the rate of com- 
bination becomes measurable above 200°. 

The alkali metals, when heated to 360° in 
hydrogen, directly absorb the gas, forming 
white solid hydrides of the type MH (Guntz, 
Compt. rend. 1896, 122, 244; Moissan, Bull. 
Soo. chim. 1902, 27, 1141; Ann. Chim. Phys. 
1906, [viii.] 6, 289, 323 ; Holt, Chem. Soc. Abstr. 
1909, ii. 807). The alkaUne-earth metals 
similarly combine with hydrogen,' yielding solid 
hydrides of the type RHj (Moissan, Btdl. Soc 
chim. 1899, [iii.] 21, 876 ; Guntz, Compt. rend. 
1901, 133, 1209). According to Winkler (Ber. 
1891, 24, 884), hydrogen combines directly with 
various finely divided metals, e.?. cerium, yttrium, 
lanthanum, obtained by reducing their oxides 
with magnesium powder. 

Hydrogen is a reducing agent, and readily 
displaces a large number of metals from their 
compounds with oxygen, sulphur, chlorine, Soo. 
Thus the oxides of copper, lead, iron, antimony, 
&c., are easily reduced to the metallic state, 
with the formation of water, when heated in a 
current of hydrogen to a more or less elevated 
temperature. Silver oxide is slowly reduced at 
ordinary temperatures, and rapidly and com- 
pletely at 100° (Colson, Compt. rend. 1900, 130, 
330), a reaction which may be used to determine 
hydrogen in gaseous mixtures. Palladous oxide 
is reduced in the cold by hydrogen (Wohler, 
Annalen, 1874, 174, 60), as also is the corre- 
sponding chloride, either in the anhydrous state 
or in solution (PhiUips, Amer. Chem. J. 1894, 16, 
255 ; Campbell and Hart, ibid. 1896, 18, 294). 

When hydrogen is passed through a solution 
of silver nitrate, sulphate or acetate, metallic 
silver is precipitated; the amount of metal 
thus separated is small compared with that left 
in solution. The reaction is carried further by 
raising the temperature, and the precipitated 
metal is very pure. Palladium, platinum, and 
gold are similarly precipitated. Under great 
pressures, such reductions are much more com- 
plete. Thus silver and mercury are quanti- 
tatively precipitated from solutions of their 
salts at ordinary temperatures under 200 atmos. 
pressure. At higher temperatures, nickel, co- 
balt, lead, and bismuth are similarly precipi- 
tated, the deposition of nickel being complete 
at 200° and 180 atmos. (IpatiefE and Wer- 
chowsky, Ber. 1909, 42, 2078). 

Occluded hydrogen {v. infra, p. 65) is capable 
of bringing about a great number of chemical 
changes that the free gas is unable to effect. 
Thus hydrogen occluded in palladium will unite 
with chlorine, iodine, and oxygen, even in the 
dark, at ordinary temperatures (Bottger, Ber. 
1873, 6, 1396). It also reduces chlorates to 
cmorideB ; nitrates to nitrites, and oven to am- 
monia ; mercuric chloride to mercurous chloride ; 
ferric salts to ferrous salts ; ferrioyanides to 
f errocyanides • and indigo-blue to indigo-white 
(Gladstone and Tribe, Chem. News, 1878, 37, 
68). A number of these reactions can be 
utilised in quantitative analysis (Chapman, 
Analyst, 1904, 29, 346). Hydrogen occluded in 
platinum or copper prodooes similai changes. 

Hydrogen also becomes much more ohemi- 
oaUy active in contact with various finely 



divided metals, such as platinum black and 
nickel, oobaJt, iron and copper reduced from 
their oxides. Thus, hydrogen and oxygen 
combine rapidly, at ordinary temperatures, in 
the presence of platinum black. The union of 
the gases is started by the heat evolved as they 
are occluded, and, once started, combination 
proceeds quickly, the metal being heated so 
much that it becomes incandescent. Similarly, 
at 400° hydrogen and iodine vapour rapidly 
unite in the presence of platinum black. 

A very general method of reduction and 
hydrogenation has been based upon the fact 
that hydrogen becomes intensely chemically 
active in the presence of finely divided nickel 
that has been just previously reduced from its 
oxide. By passing the vapours of a large 
number of substances, mixed with hydrogen, 
over reduced nickel at quite moderate tempera- 
tures, reductions are easily effected; thus 
nitrous oxide produces nitrogen and water, 
nitric oxide and nitrogen peroxide are reduced 
to ammonia, and the oxides of carbon are con- 
verted into methane. Organic nitro compounds, 
fatty or aromatic, are reduced to amines. Un- 
saturated fatty hydrocarbons are transformed 
into parafSns, while benzene and numerous 
derivatives are easily converted into hexahydro- 
benzene and its substitution-products. Alde- 
hydes and ketones are reduced to alcohols with 
remarkable ease. The nickel is not altered, and 
permits of hydrogenation being carried on 
indefinitely (Sabatier and Senderens, Compt. 
rend. 1897, 124, 1358; 1899, 128, 1173; 1900, 
130, 1559, 1628, 1761 ; 131, 140 ; 1901, 132, 210, 
566, 1264 ; 133, 321 ; 1902, 134, 614, 689, 1127 ; 
135, 87, 225; 1903, 136, 738, 921. 983; 137, 
301, 1025; 1904, 138, 467, 1257; 1905, 140, 
482; BuU. Soc. chim. 1905, [iii.l 33, 263 ; Ann. 
Chim. Phys. 1905, [viii.] 4, 319, 433 ; Sabatier 
and Mailhe, Compt. rend. 1903, 137, 240 ; 1904, 
138,407,245; 1905,140,350; 1906,142,653; 

1907, 144, 824, 955, 784, 1086; 145, 18, 1126; 

1908, 146, 457, 1193 ; Ann. Chim. Phys. 1909, 
[vui.] 16, 70). 

Certain chemical systems which lead to the 
liberation of hydrogen are capable of acting as 
reducing agents -when another substance^ is 
added to them that is capable of being reduced. 
Thus a solution of potassium chlorate remains 
unaffected when hydrogen is passed through it, 
but reduction to chloride readily occurs if zinc 
and sulphuric acid are added to the solution. 
Other systems are furnished by the alkali 
metals or their amalgams in contact with water, 
which are capable, among other things, of re- 
ducing aldehydes and ketones to alcohob ; and 
zinc, iron, or tin, with either hydrochloric, sul- 
phuric, or acetic acid, systems which are capable 
of reducing nitro compounds to amines, Jcc. 
Hydrogen evolved from such systems therefore 
appears to possess an activity superior to that 
of the ordinary gas;. it is termed nascent 
hydrogen. 

The superior activity possessed by hydrogen 
at the moment of its liberation is supposed by 
some chemists to be due to the fact that the gaS^ 
is liberated in the atomic state, and is therefore 
more capable of entering into chemical reactions 
than after it has assumed the moleoulai state, 
since the combination of atoms to form mole- 
cules is accompanied by the degrading of s 



HYDROGEN. 



65 



certain amount of energy. That this cannot be 
a full explanation is seen, however, by the fact 
that a reduction effected by one system evolving 
nascent hydrogen is not necessarily effected by 
another system, e.g. the system zinc and dilute 
sulphuric acid wUl reduce chlorates to chlorides, 
but the system sodium-amalgam and water 
will not. 

Adsorption of hydrogen by metals. In 1863, 
Deville and Troost (Compt. rend. 1863, 57, 894) 
observed that red-hot platinum and iron were 
permeable to hydrogen. Upon further investi- 
gating this subject, Graham (Proc. Roy. Soc. 
1867, 15, 223 ; 1868, 16, 422 ; 1869, 17, 212, 
500) found that palladium possessed this 
property in a much higher degree, and, further, 
he showed that there was no need to assume a 
porosity in the structure of these metals to 
accoimt for this phenomenon, but that it was 
due to the fact that such metals absorb hydro- 
gen, yielding substances which still retain 
metaJlic lustre and characteristic metallic 
properties, but which readily evolve the ab- 
sorbed gas under altered conditions. To this 
property, Graham gave the name occlusion. 
It may be studied by placing the metal within 
■a porcelain tube, glazed inside and out, evacu- 
ating it by means of a mercury pump and 
heating to redness. Hydrogen is then admitted 
and allowed to flow over the metal while it cools. 
The tube is then evacuated again and the 
contents heated to redness once more, by 
which means the occluded hydrogen is expelled 
from the metal, and may be pumped off and 
measured. 

The amount of hydrogen adsorbed depends 
to some extent on the physical condition of the 
metal. In one experiment, a palladium wire 
was found by Graham to absorb 935 times its 
own volume of hydrogen. Mond, Ramsay, and 
Shields (Phil. Trans. 1895, A, 186, 657 ; 1897, 
A, 190, 129 ; 1898, A, 191, 105) have shown that 
palladium black adsorbs at the ordinary tem- 
perature 873 to 889 volumes of hydrogen and 
that palladium wire and sponge adsorb a 
similar amount. Palladium-hydrogen readily 
evolves hydrogen in a vacuum, that prepared 
from the ' black ' at the ordinary temperature, 
while the substance obtained from the foil 
requires warming to 1 00°. In all cases, however, 
a red heat is required to drive off the last traces 
of gas. Even at a red heat, however, palladium 
still adsorbs large quantities of hydrogen if the 
pressure is sufficiently increased (Dewar, Chem. 
. Soc. Proc. 1897, 192). 

Palladium readily adsorbs 935 vols, of 
hydrogen if it is employed as negative electrode 
in a water voltameter. Should the electrolysis 
be continued beyond this point, the metal 
becomes supersaturated with gas ; the excess 
is, however, evolved as soon as the current 
ceases (Thoma, Zeitsch. physikal. Chem. 1889, 
3, 69). 

CoUoidal palladium and platinum solutions 
adsorb hydrogen very readily and in large 
amounts (Kernot and Niguesa, Rend, accad. 
Sci. Fis. Mat. Napoli, 1909, [iii.] 15, 168). Various 
other metals, e.g. iron, nickel, cobalt, gold, and 
copper, also adsorb small quantities of hydrogen. 

The process of occlusion is accompanied by 
an evolution of heat, 4370 calories being evolved 
per gram of hydrogen occluded ; the thermal 
Vol. ni.—T. 



effect is the same for each successive fraction of 
gas absorbed (Favre, Compt. rend. 1869, 68, 
1306 ; Mond, Ramsay, and Shields, I.e.). 

The nature of the substances formed when 
hydrogen is occluded by metals has not yet been 
determined with certainty. The metals are 
unaltered in appearance, and such physical 
properties as thermal and electrical conductivity, 
sp.gr., and tenacity are only slightly diminished. 
Graham was of opinion that no oheinical union 
occurs, but that the hydrogen assumes the solid 
form and acts as a quasi-metal. This adsorbed 
form of hydrogen he proposed to call hydro- 
genium. 

From the expansion of aUoys of palladium 
with platinum, gold, and silver, when charged 
with hydrogen, Graham calculated the sp.gr. of 
hydrogen to be 0-733 ; subsequent determina- 
tions by Dewar gave the figure 0-620, a figure 
which does not compare at all with the actual 
sp.gr. of solid hydrogen. 

Troost and Hautefeuille (Compt. rend. 1874, 
78, 686) believed that their experiments indi- 
cated the existence of a definite compound, 
PdaH, whflst Dewar (Chem. News, 1897, 76, 274) 
suggested the existence of PdjHj. The fact 
that when fully charged with hydrogen, the 
composition of palladium-hydrogen approxi- 
mates closely to this latter formula is, however, 
almost the only evidence that can be adduced 
in support of the existence of this compound 
(Mond, Ramsay, and Shields, I.e.). The experi- 
ments of Hoitsema (Zeitsch. physikal. Chem. 
1895, 17, 1) have shown that between 20° and 
200° no definite compounds of palladium and 
hydrogen exist ; at constant temperature the 
relationship between the vapour tension of the 
system palladium-hydrogen and the percentage 
of hydrogen in the solid phase is such, however, 
as would be expected if two partially-miscible 
solid solutions of hydrogen in the metal are 
formed, the miscibility of which increases with 
rise of temperature. 

The meteoric iron of Lenarto, containing 
91 p.c. of iron, yields 2-85 times its volume of 
occluded gas, mainly hydrogen (Graham, Proc. 
Roy. Soc. 1867, 16, 502). Since under ordinary 
pressure iron absorbs only half its volume of 
hydrogen, this would seem to show that the 
meteorite has come from an atmosphere con- 
taining hydrogen under a pressure much greater 
than that of our own atmosphere, thus affording 
a confirmation of the conclusions drawn from 
spectroscopic observations regarding the exist- 
ence of dense and heated hydrogen atmospheres 
in the sun and fixed stars. 

Atomic weight of hydrogen. This has been 
determined by measuring the ratio of the com- 
bining weights of oxygen and hydrogen. Since 
this ratio is of fundamental importance, a very 
considerable amount of attention has been 
directed towards its accuratb measurement. 
The methods used may be grouped under two 
headings: (o) synthesis of water ; and (5) deter- 
minations of the relative densities of hydrogen 
and oxygen. 

(a) The classical method, first employed by 
Dulong and Berzelius (1820), and used later 
by Dumas (Ann. Chim. Phys. 1843, [iii.] 8, 189) 
in his elaborate series of determinations, con- 
sists in reducing heated cuprio oxide in a 
stream of pure, dry hydrogen, and estimating 



66 



HYDROGEN. 



the water produced and the loss in weight 
experienced by the cupric oxide. The result 
obtained by Dumas, viz. H : O :: 1 : 15'9607, 
corroborated as it was by the experiments of 
Erdmauu and Marchand (J. pr. Chem. 1842, 26, 
461) was for many years accepted as the true 
value; but subsequent work has shown that 
this result deviates considerably from the truth, 
and has disclosed numerous sources of error 
in the older determinations. The method of 
Dumas, with various modifications^ has been 
used by Cooke and Richards (Amer. Chem. 
J. 1888, 10, 81, 191) ; Keiser {ibid. 1888. 10, 
249); Noyes {ibid.. 1889, 11, 155; 1890, 12, 
441); Dittmar and Henderson (Proc. Roy. 
Soo. Glasgow, 1891, 22, 33), and Leduo (Compt. 
rend. 1892, 115, 41) ; their results are given 
in the table below. 

The synthesis of water has been effected by 
other methods than the above. In 1889, 
Rayleigh (Proc. Roy. Soo. 45, 425) weighed pure 
hydrogen and oxygen in glass globes, mixed 
them and then gradually exploded the mixture 
in a eudiometer. The residual gas was then 
analysed, and hence the ratio of hydrogen to 
oxygen determined. The first complete quan- 
titative syntheses of water, in which both gases 
were weighed separately, and afterwards in 
combination, are due to Morley (Smithsonian 
Contributions to Knowledge, 1895, 29). The 
hydrogen was weighed in palladium (a method 
due to Keiser) and the oxygen in compensated 
globes, after the manner of Regnavdt. After 
weighing, the gases were burned by means of 
electric sparks in a suitable apparatus, from 
which the unburned rpsidue could be withdrawn 
for examination. Finally, the apparatus con- 
taining the water produced was closed by fusion 
and weighed. 

The syntheses of water by Keiser (Amer. 
Chem. J. 1898, 20, 733) were effected by the direct 
oxidation of hydrogen occluded in palladium ; 
the hydrogen, oxygen, and water were all deter- 
mined. The experiments recorded in the 
elaborate investigation by Noyes (J. Amer. 
Chem. Soc. 1907, 29, 1718) were performed 
partly by this method and partly by the method 
employed in his earlier work {v. supra). A 
novel, but indirect method for measuring the 
ratio of oxygen to hydrogen has been employed 
by Thomson (Zeitsoh. anorg. Chem. 1895, 11, 

The results of these experiments are collected 
in the following table : — 









At.wt. 


Experimenter 


Date 


Ratio 0/H 


of Hyd. 
(0=16) 


Dumas . 


1842 


15-9607 


1-00246 


Erdmann & Marchand 


1842 


15-9760 


1-00156 


Cooke & Richards 


1888 


15-8690 


100825 


Keiser 


1888 


15-9514 


1-00305 


Noyes 


1889 


15-8966 


1-00650 


Dittmar & Henderson 


1891 


15-8677 


1-00834 


Leduo 


1892 


15-8810 


100750 


Rayleigh . 


1889 


15-8900 


1-00692 


Morley . 


1895 


15-8790 


1-00762 


Keiser 


1898 


15-8799 


1-00756 


Noyes 


1907 


15-8745 


1-00783 


Thomson . 


1895 


15-8690 


1-00825 



The weighted mean of these results is 
H= 1-00769 according to Clarke (A Recalcula- 
tion of the Atomic Weights, 3rd edit. 1910, 29). 

(6) The ratio of the densities of oxygen and 
hydrogen is, subject to a correction to be men- 
tioned later, equal to the ratio of their atomic 
weights. The first accurate measurements of 
these densities were made by Dumas and 
Boussingault in 1841 (Compt. rend. 12, 1005) ; 
the results obtained four years later by Regnault 
{ibid. 20, 975) were adopted as standard values 
for many years, and gave for the ratio a value 
of 15-9611. The remarkable agreement of this 
figure with that deduced from Dumas' synthesis 
of water is only, however, accidental, for in 
1885, Agamennone, and independently, Ray- 
leigh in 1888 (Proc. Roy. Soc. 43, 356) pointed 
out a serious error in all previous determinations 
of gaseous densities, owing to the fact that the 
glass globes in which the gases are weighed are 
elastic, and shrink to a measurable extent when 
evacuated. The effect of neglecting to correct 
for this shrinkage is that the apparent weight of 
gas is slightly lower than its true value. The 
corrected vdue for the density ratio from 
Regnault's experiments is 15-9105 (Crafts, 
Compt. rend. 1888, 106. 1662). 

In recent years, the densities of hydrogen 
and oxygen have been frequently determined 
with the utmost care ; v. Rayleigh (Proc. Roy. 
Soc. 1892, 60, 448; Cooke, Amer. Chem. J. 
1889, 11, 509); Leduo (Compt. rend. 1891, 113, 
186); Thomsen (Zeitsch. anorg. Chem. 1896, 
12, 4) and especially Morley (Smithsonian Contri- 
butions, 1895). The table below summarises 
the results obtained : — 



Experimentei 


Date 


Density 
ratio 0/H 


Dumas & Boussing 


ault . 1841 


15-9015 


Regnault 


1845 


15-9105 


Rayleigh 




1888 


15-8840 


Rayleigh 




1892 


15-8820 


Cooke . 




1889 


15-8900 


Leduo . 




1891- 


15-9060 


Morley 




1895 


15-8955 


Thomsen 




1896 


15-8878 



The weighted mean is 15-8948 (Clarke. Uc). 

This* result is subject to a slight correction 
for the fact that hydrogen and oxygen do not 
combine together by volume exactly in the ratio 
of two to one ; according to Morley {l.c.), the 
exact ratio is 2-00274 (c/. Scott, Phil. Trans. 
1893, 184, 543 ; Leduo, Compt. rend. 1892, 176, 
311 ; Rayleigh. Proc. Roy. Soc. 1904, 73, 163). 
Correcting the above mean value for the density 
ratio in accordance with this result, the figure 
15-8726 is obtained, which leads to the value 
1-00803 for the atomic weight of hydrogen on 
the oxygen scale. 

According to Clarke {I.e.), the probable mean 
derived from the results of methods (o) and (6) 
combined, is H = 1 -00772. The value at present 
adopted is H= 1-008. 

Applications of hydrogen. Hydrogen is used 
in conjunction with oxygen for the production 
of the Drummond or oxy-hydrogon Ume light. 
For this purpose, the gases are compressed in 
iron bottles furnished with taps and jets, so that 



HYDROGEN. 



67 



they can be allowed to escape, and butned as 
required. They are allowed to impinge on a 
oyUndet of lime which is thereby heated to 
whiteness, and gives a light almost equal to the 
electric arc. 

For the autogenous welding of metals, the 
working of platinum, and the manufacture of 
laboratory utensils and mercury vapour lamps 
from fused quartz, hydrogen in the form of the 
oxyhydrogen blowpipe flame is used in large 
quantities, although it has here to meet the 
competition of acetylene, which is cheaper and 
readily obtainable as required from calcium 
carbide. 

Aviogenona soldering. — ^This process is much 
used for uniting the edges of the sheets of lead 
which are employed in making vessels for the 
purpose of holding acids. Joints made in this 
way are much more durable than those made 
with solder. The apparatus for this purpose is 
made so that hydrogen can be generated at 
pleasure, and when not in use the pressure of 
gas inside the apparatus lifts the acid out of 
contact with the zinc. The hydrogen generator 
consists of a cylindrical copper vessel lined with 
lead ; there is an upper and lowei chamber 
connected by a -pipe, and they are filled with 
arrangements wmoh admit of easy renewal of 
acid or zinc and the removal of the zinc sulphate 
formed. The apparatus gives a very constant 
flame, which may be used with advantage in 
soldering lead in the way which is practised in 
the construction of sulphuric acid chambers. 
The hydrogen is delivered from a platinum- 
tipped nozzle through which a jet of aii; also 
issues from a foot bellows ; this is effected by 
attaching the nozzle by means of india-rubber 
tubing to a tube which branches out V-shaped 
into two limbs each provided with a stopcock ; 
each of these limbs is provided with an india- 
rubber tube, one of which is attached to the 
bellows and the other to the delivery tube of the 
hydrogen generator. The operato,r can, there- 
fore, carry the nozzle in his hand and direct the 
flame where he pleases, and by means of the 
etopoock he can readily regulate the supply of 
ait or hydrogen. 

Tungsten lamps. — ^The manufacture of tung- 
sten filament lamps requires a regular supply of 
hydrogen to prepare the inert atmosphere in 
which the filaments are heated to a high tempera- 
ture during the final treatment. It is almost 
the universal custom to employ a mixture of 
equal volumes of hydrogen and nitrogen when 
the filaments are electrically heated to whiteness. 
Since incandescent tungsten filaments are very 
sensitive to oxidation, it is of great importance 
that the hydrogen employed should be of a high 
degree of purity. The process devised by Lane 
(». infra) is frequently adopted for obtaining the 
gas, since besides preparing hydrogen, it also 
admits of nitrogen being collected. 

Hydrogen for balloons. — Soon after Caven- 
dish published his researches on ' inflammable 
air,' Charles, in 1783, suggested the applioa- 
tion of hydrogen for the inflation of balloons. 
Montgolfier had, during the same year invented 
the balloon which he inflated with rarefied air. 
In hydrogen, however, Charles recognised a 
much more suitable means of inflation, although 
the cost was very considerable, 600 lbs. of sul- 
phuric acid and twice that amount of iron being 



consumed in the inflation of a balloon about 
13 feet in diameter. 

The first balloon sent up from English soil, 
on Nov. 25, 1793, was inflated with hydrogen. 
In the following year, the French Government 
instituted a series of experiments at Meudon ' 
under Guyton de Morveau, ConteUe, and Comte 
with the view of perfecting the balloon for recon- 
noitring, signalling, and other warlike.purposes. 
For the preparation of the hydrogen, Guyton de 
Morveau suggested a method invented by 
Lavoisier, that of passing steam over red-hot 
iron, and a furnace was accordingly built,*which 
after many trials, was capable of producing suf- 
flcient gas to fill a balloon, 27 feet in diameter, 
in 4 hours. This balloon, with one filling, re- 
mained in use for a month. 

Balloons inflated with hydrogen were used in 
the American Civil War in 1861. The gas was 
generated from old scrap iron and sulphuric acid 
in wooden tanks lined with lead : the apparatus 
was carried from place to place on two carts. 

In 1878, Giffard made a gigantic captive bal- 
loon for the Paris Exhibition. It was spherical 
in form, 118 feet in diameter, and had a capacity 
of 882,902 cb. feet. To fill this great aerial ship 
with hydrogen gas, 190 tons of sulphuric acid 
and 80 tons of iron were consumed (Jour. United 
Service Inst. 27, 735-756). 

Hydrogen was also used in the Soudan War 
for inflating balloons. For this purpose, the gas 
was compressed in strong iron cylinders, 12 feet 
long by 1 foot in diameter ; these Vrere for a 
reserve supply, and weighed halt a ton each. A 
gas factory and pumping station were put up. 
To meet first requirements about 100 lighter 
cylinders, 9 feet long, and containing 120 feet of 
gas in a compressed condition, were taken out ; 
these were so constructed as to be easily carried 
by men. One waggon containing a ton of stores 
was sufficieht for a balloon ascent ; a volume of 
gas occupying 4,150 feet was suf&cient to lift a 
man 1,000 yards (lUus. Nav. andMil. Gaz. 11, 172). 

At the present time it is highly important 
for the maintenance of large dirigible balloons 
to be assured of a regular supply of pure hydro- 
gen gas. The chief drawback to the use of 
hydrogen is its high rate of diffusion, a drawback 
which is being minimised by improvements in 
the manufacture of balloon fabrics. 

Most of the hydrogen now used for inflating 
the gas bags of dirigible airships is produced 
either electrolytically or by the action of steam 
on red-hot iron. The former method has been 
largely developed in Germany, and depends for 
success upon a cheap supply of electrical energy. 
It yields pure hydrogen and the plant requires 
very little attention. 

The other method is now used in this country 
as described by Lane (Eng. Pat. 17591, 1909) ; 
iron is heated to redness in a current of steam, 
and the oxide produced is reduced by heating in 
a current of water gas, the resulting metal being 
used again. By carrying on the reduction 
process in a number of the retorts and the 
preparation of hydrogen simultaneously in the 
others, it is possible to make the production of 
hydrogen more or less continuous. 

The need for rapid convenient methods for 
preparing hydrogen for military purposes has 
led to the introduction of the ' hydroUth ' and 
' hydrogenite ' processes for its preparation. 



68 



HYDBOGEN. 



which are employed byHhe French army. In 
the former process, ' hydrolith,' a white crys- 
talline powder consisting of calcium hydride 
(90 p.o. pure, the remainder being oxide and 
nitride), is decomposed by water. One kilo, 
of the solid yields about 1 cubic metre of hydro- 
gen. The portable apparatus used by the 
French army can fill an army dirigible in 4 hours. 
For speed, convenience, and reliability, hydro- 
lith is unexcelled, but its high cost renders its 
use almost prohibitiTe for private aeronautics. 
' Hydrogenite ' is a compressible powder, con- 
sisting of ferrosilicon (90-95 p.o. Si) 25 pts., 
sodium hydroxide 60 pts., and slaked lime 
20 pts. (Sander, Chem. Zeit., 1911, 35, 1273); 
when ignited by a suitable ' match,' it 
reacts spontaneously, much as do thermit 
mixtures, with the evolution of hydrogen and 
the production of sodium and calcium silicates. 
The material is hygroscopic, and is sold in a 
compressed cake in metal cartridges. One 
kilo, of substance yields from 270 to 370 Utres 
of hydrogen. (For the method of using the 
substance for filling balloons, v. Jaubert, Rev. 
ge'n. chim. 13, 341, 357; and cf. D. E. P. 
218257, 1908.) 

HYDROGENIUM v. Hydboqbn. 

HYDROGEN PEROXIDE. Symbol B.^0^. 
This compound was discovered in 1818 by 
Thenard. It occurs at times in small quan- 
tities in the atmosphere, in dew, in rain, and in 
snow (Schone, Ber. 1874, 7, 1695 ; ibid. 1893, 
26, 3011 ; ibid. 1894, 27, 1233 ; Zeitsoh. anal. 
Chem. 1894, 33,137); but Hosva (Ber. 1894, 27, 
920) maintains that the tests used fox detecting 
it in these media would also be given by the 
oxides of nitrogen, which are always present. 
It is said to be contained in many green 
plants (Bach, Compt. rend. 1894, 119, 1218; 
Chodat and Bach, Ber. 1902, 35, 1275, 3943 ; 
1903, 36, 1756 ; 1904, 37, 36). It Is also con- 
tained in solution in the water produced by the 
combustion of hydrogen in oxygen (Schuller and 
Bach, Compt. rend. 1897, 124, 951 ; Keiser and 
McMaster, Amer. Chem. J. 1908, 39, 96), and 
in the flames of alcohol, coal gas, ether, and 
carbon disulphide (Engler, Ber. 1900, 33, 1109). 

Hydrogen peroxide is formed in small quan- 
tities in the electrolysis of aqueous solutions 
(Richarz, Zeitsch. anorg. Chem. 1903, 37, 75; 
Ber. 1909, 42, 4674 ; Biesenfeld and Reinhold, 
ibid. 2977); when aTeslabrush discharge, or the 
silent electric discharge is passed through water 
vapour (Findlay, Zeitsch. Elektrochem. 1906, 
12, 129 ; Nemst, ibid. 1905, 11, 710 ; Lob, Ber. 
1908, 41, 1517; Binge and Fischer, ibid. 945); 
during the slow oxidation of many metals, 
particularly their amalgams, in the presence of 
water (Traube, Ber. 1893, 36, 1471; Smith, 
Chem. Soc. Trans. 1906, 481; Barnes and 
Shearer, J. Phys. Chem. 1908, 12, 155, 468; 
Rankin, Proc. Boy. Soc. 1910, B, 82, 78); 
with zinc amalgam and in the presence of an 
alkaline earth a better yield is said to be ob- 
tained (D. E. P. 48542; J. Soc. Chem. Ind. 
1890, 213). 

Hydrogen peroxide is also formed under 
several other circumstances, as, e.g., when 
freshly-ignited bone black is moistened with as 
much water as it will take up, and exposed to 
light and air. Even in a few minutes a percep- 
tible amount of hydrogen peroxide is formed 



(Dingl. poly. J. 256-519). A carbonic oxide 
flame (when the gas has been previously passed 
through water) is said to produce it in quantity, 
or if burnt in contact with the surface of water 
the same effect is produced (J. Soc. Chem. Ind. 
1884, 496). 

When turpentine oil or any other hydro- 
carbon containing a terpene is oxidised by air oi 
ozone in the presence of water, hydrogen 
peroxide is formed and passes into solution in 
the water. In this way it is possible to prepare 
a solution of two volumes strength, that is to 
say, of such a strength that when fully decom- 
posed it is capable of yielding twice its own 
volume of oxygen gas (Kingzett, Eng. Pat. 
12274; J. SocChem. Ind. 1898, 691). 

It is also said to be produced by the oxida- 
tion of a number of organic compounds, such as 
urine, ether, &c., in direct sunlight (Richardson, 
Chem. Soc. Trans. 1893, 1110; ibid. 1896, 1349). 

Preparation. — 1. By passing a copious stream 
of well- washed carbon dioxide throu^ cooled dis- 
tilled water to which is added very gradually pure 
barium peroxide, finely powdered and suspended 
in water. The cautious addition of the barium 
peroxide is necessary, as an excess of it would 
cause the decomposition of any hydrogen per- 
oxide formed, with evolution of oxygen and 
formation of water. After allowing the gas to 
pass some considerable time, ~ the barium 
carbonate is filtered ofl, and the solution 
evaporated in vacud over sulphuric acid imtil it 
acquires a syrupy consistency ; 

BaOa-|-COj+H20=Ha02-fBaCO, 
(D. B. P. 179771, 179826 ; J. Soc. Chem. Ind. 
1906, 117). 

2. The preparation is also effected by the 
decomposition of barium peroxide with hydro- 
fluoric, siUcofluorio, phosphoric, sulphuric, 
borofluoric, or hydrochloric acid, of which the 
last is to be preferred, owing to its cheapness, 
whilst the purest peroxide is obtained with 
phosphoric or borofluoric acids. The barium 
peroxide, which must be of the purest quality 
and very finely ground, is made into a thin 
paste with water, and introduced very gradually 
into the acid solution, the temperature of which 
must never exceed 10°-15°, and must be con- 
stantly agitated. When the solution is nearly 
neutralised, the liquid is decanted from the 
precipitate, and freed from iron and aluminium 
oxides by treatment with sodium phosphate 
solution, then with sufficient barium peroxide 
or waste barium oxide to make the liquid 
neutral, lastly with ammonia, after which it is 
rapidly pumped through a filter press. It is 
then freed from dissolved baryta by the addition 
of sodium sulphate. The most stable peroxide 
is that prepared with phosphoric acid, and 
contains a small amount of that acid in the free 
state (Chem. Zeit. 9, 949 and 976 ; Bourgougnon, 
J. Amer. Chem. Soc. 12, 64; Fawsitt, J. Soc. 
Chem. Ind. 1902, 229 ; see also Eng. Pats. 
10476, 3628, 21333 ; J. Soc. Chem. Ind. 1891, 
482; ibid. 1892, 707; ibid. 1900, 70). Nitric 
acid has also been employed (Fr. Pat. 359523 ; 
J. Soo. Chem. Ind. 1906, 374). 

3. Hydrogen peroxide has also been con- 
veniently, but not so cheaply, prepared by 
treating sodium peroxide with hydrofluoric or 
hydrochlorio acids (U.S. Pat. 692139; J. SOc. 
Chem. Ind. 1902, 364 ; Fororand, Compt. rend. . 



HYDROGEN PEROXIDE. 



1899, 129, 1246; Merok, Chem. Zentr. 1904, 
ii. 67) ; and by treating persulphates, peicaibon- 
atea, and perborates, obtained by eleotiolysis 
of tbe ordinary acids with dilute acids ( Jaubert, 
Chem. Zentr. 1905, ii. 99 ; D. R. PP. 217538, 
217539, 195351, 199958, 179826 ; J. Soo. Chem. 
Ind. 1906, 379; ibid. 1906, 321, 379; ibid. 

1908, 448, 856 ; ibid. 1910, 489). 

Pure concentrated solutions of hydrogen 
peroxide have been prepared by the action of 
alcohol and dilute sulphurio acid on sodium 
peroxide in earthenware, glass, or lead vessels at 
—10°. The alcohol is then removed by distilla- 
tion in vacua (Dony-H^nault, Fr. Pat. 403294 ; 
J. Soc. Chem. Ind. 1909, 1314). A mixture of a 
perborate with an equivalent amount of a dry 
solid organic oi inorganic acid, or of a solid 
acid salt has been prepared, which, on treatment 
with water, yields hydrogen peroxide (Fr. Pat. 
401911 ; J. Soo. Chem. Ind. 1909, 1198). 

Hydrogen peroxide has also been prepared 
by blowing superheated steam against a heated 
body (Eng. Pat. 20868, 1907 ; Fr. Pat. 382189, 
1907 ; D. R. P. 205262, 1908 ; J. Soc. Chem. 
Ind. 1906, 808 ; ibid. 1908, 123, 226 ; ibid. 

1909, 140 ; Fischer and Ringe, Ber. 1908, 41, 
945), and by blowing moist air against a spark 
or arc discharge (D. R. PP. 197023 ; 228425 ; J. 
Soc. Chem. Ind. 1910, 1462). 

(For other methods see D. R. P. 185597; 
Bomemann, Zeitsch. anorg. Chem. 34, 1 ; 
Fr. Pat. 371043; Soheuer and Vemet, Bull. 
Soo. Ind. Mulhouse, 1907, 77, 336 ; ibid. 1908, 
78, 184, 187 ; J. Soo. Chem. Ind. 1910, 1306 ; 
Fr. Pat. 415361.) 

Commercial hydrogen peroxide is liable to 
contain hydrochloric, sulphuric, phosphoric, 
and hydrofluoric acids, alumina, lime, magnesia, 
potash, and soda, derived from water or other 
materials used in its manufacture, whilst baryta 
and traces of iron, copper, lead, and manganese 
are sometimes fotmd if it has been carelessly 
made. 

When these last are present, the product is 
tolerably stable only if it be sufficiently acid, 
though even then it is less stable than in the 
absence of these impurities. 

The commercial liquid of so-called 10 volume 
or about 3 p.o. strength may be purified by the 
addition of about J p.c. of concentrated phos- 
phoric acid (preferably pure) to precipitate iron, 
copper, lead, and manganese, and prevent the 
subsequent formation of their peroxides which 
would otherwise take place. Saturated baryta 
water (hot or cold) is then added very gradually, 
until neutrality is reached. No excess must be 
used or hydrated BaOj will be precipitated, 
which will induce decomposition of a portion of 
the hydrogen peroxide. 

The clear liquid is now drawn off, and is 
poured into an excess of cold saturated baryta 
water, when hydrated BaOj is thrown down, and 
is then washed until no metal except barium 
can be detected in the washings. 

The BaOj is then suspended in water and 
added drop by drop to a solution consisting of 
90 parts of distilled water to 10 parts of pure 
concentrated sulphuric acid until only traces of 
acid remain free; these are best removed by 
weak baryta water, for an accidental excess of 
BaOg wUl induce decomposition of some of the 
already formed hydrogen peroxide, whilst an 



excess of BaO will have no such effect. The 
barium sulphate is allowed to settle, and the 
clear liquid drawn off, if found free from both 
barium and sulphuric acid. The resulting pro- 
duct is about 3 p.c. strength, fairly stable and of 
great purity (Mann, Chem. Zeit. 12, 857 ; J. Soc. 
Chem. Ind. 1889, 640). 

The commercial solutions can be concen- 
trated to 95-99 p.c. by evaporating in air at 
75° to 20 p.c. strength, then imtiocjuj to 50-55 p.c, 
after which it is treated with ether, in which 
the peroxide is readily soluble. The ethereal' 
extract is then carefully distilled and fraction- 
ated in vacud (Wolffenstein, Ber. 1894, 27, 3307 ; 
Staedel, Zeitsch. angew. Chem. 1902, 15, 642; 
Tyrer, I.e. ; Merck, I.e.]; also by distilling the 
solutions at a temperature below 85° in a power- 
ful current of an inert gas (D. R. P. 219154). 

The concentrated solution remains liquid at 
—20°, but when immersed in a mixture of ether 
and carbon dioxide, it crystallises to a solid 
mass, consisting of the anhydrous peroxide. 
Clear colourless crystals of the latter can also 
be obtained by introducing a fragment of the 
solid into a freshly prepared 90-80 p.c. solution 
at —8° (Staedel, I.e.). Hydrogen peroxide 
should be kept in paraffin or paraffin-lined vessels. 

A number of substances have been proposed 
as suitable for increasing the stability of hydro- 
gen peroxide, such as sulphurio or phosphoric 
acids (Tyrer, Pharm. J. 63, 100)^ sodium pyro- 
phosphate (Eng. Pat. 23676; J. Soc. Chem. 
Ind. 1910, 152); organic substances such as 
alcohol, ether, glycerol, &o. (Sanders, Bull. 
Soc. Ind. Mulhouse, 1897, 95; Freyes, ibid. 97 
Eng. Pat. 15993); 1 gram pure crystalline 
naphthalene to 1 litre of solution (Zinno, Bull. 
Soc. Ind. Mulhouse, 1895, 78); gallic acid or 
pyrogallol (Arndt, D. R. P. 196370); uric or 
barbituric abids (D. R. PP. 216263, 203019, J. 
Soc. Chem. Ind. 1908, 1204; ibid. 1909,1314); 
phenacetin or an amide or imide oi acetyl 
derivative of an aromatic base (J. Soo. Chem. 
Ind. 1906, 1219); oxaUo acid (Fischer, Pharm. 
Zentr. 1907, 48, 57, 79). 

According to Allain (J. Pharm. Chim. 1906, 
24, 162) sodium or calcium chloride in the 
proportion of 1 p.o. are more efficient preserva- 
tives for medicinal hydrogen peroxide than 
sulphurio or phosphoric acids. They are also 
less objectionable than the latter, from a 
therapeutic point of view. See also Kingzett 
(J. Soc. Chem. Ind. 1890, 3). 

The amount of hydrogen peroxide in an 
aqueous solution may be conveniently deter- 
mined by titration with a solution of potassium 
permanganate containing 7-9 grams IMnOj per 
litre. 2 c.c. of hydrogen peroxide solution 
are introduced into a graduated tube of 35 c.c. 
capacity, 5 or 6 drops of hydrochloric acid are 
added, and then the solution of permanganate is 
gradually introduced with constant agitation 
until the contents of the tube are of a red on 
brownish colour; the quantity of solution is 
then read off, 5 c.c. representing 1 p.o. of hydro- 
gen peroxide. The results are accurate to 
within 0-1 p.c. and can be obtained in » few 
minutes ' (Chem. Zeit. 9„ 940 and 976). 

1 The reaction between hydrogen peroxide and 
potassium permanganate in acid solution may be 
utilised for preparing oxygen gas. In this way a good 
stream of tolerably pure oxygen may be readily 



70 



HYDROGEN PEROXIDE. 



In the presence of persulphates, however, 
accurate results can only be obtained by using 
a minimum volume of solution, a large excess of 
sulphuric acid and performing the titration very 
rapidly ; for this purpose an excess of per- 
manganate is added, and the latter is then 
titrated back with sodium thiosulphate (Friend, 
Chem. Soc. Trans. 1904, 597, 1533 ; ibid. 1905, 
1367 ; Skrabal and Vacek, Chem. Zeit. 1910, 34 ; 
Kep. 121). 

If oxaho acid is present, this must first be 
removed (Sisley, J. Soc. Chem. Ind. 1901, 1028 ; 
ibid. 1904, 685 ; Roche, ibid. 1902, 190). 

Another and more accurate method is to 
strongly acidify the solution of hydrogen peroxide 
with sulphuric or hydrochloric acid, then add a 
solution of potassium iodide free from iodate, and 
determine the iodine liberated by means of a 
standard solution of sodium thiosulphate (King- 
zett, Chem. Soc. Trans. December, 1880, and 
The Analyst, 1888, 13, 62 ; Rupp, Arch. Pharm. 
238, 156; Plane's, J., Pharm. Chim'. 1904, 20, 
638). 

Hydrogen peroxide can also be estimated by 
titrating against ferrous ammonium sulphate in 
presence of ammonium sulphate and phosphoric 
acid (Mathewson and Calvin, Amer. Chem. J. 
1906, 36, 113); and by estimating the quantity 
of arsenious acid it will oxidise to arsenic acid 
(Griitzner, Arch. Pharm. 237, 705). 

According to Dehn the most rapid, conve- 
nient, and accurate method of estimating hydro- 
gen peroxide is to measure the volume of oxygen 
evolved when a known quantity of the solution 
Is treated with sodium hypobromite in a special 
apparatus described by him (J. Amer. Chem. 
Soo. 1907, 29, 1315). The following reaction 
takes place HjOa+NaBrO=NaBr-fH20+02. 
By this method the presence of preservatives 
may be neglected. (For the estimation of the 
peroxide retained by fabrics, eee Scheuer and 
Vernet, I.e.) 

To determine the quantity of acid present 
in commercial hydrogen peroxide, the best 
method is by direct titration in the cold, with 
N/10 sodium hydroxide solution, using phenol- 
phthalein as indicator (Brown, J. Ind. Eng. 
Chem. 1910, 377 ; Endemann, Zeitsch. angew. 
Chem. 1909, 22, 673 ; Luning, ibid. 1549). 

Properties. — Pure anhydrous hydrogen per- 
oxide forms colourless prismatic crystals; 
m.p. —2°, b.p. 84''-85768 mm., 69-2726 mm. It 
forms a syrupy transparent acid liquid, which is 
colourless in thin layers, but bluish-green when 
viewed in bulk (Spring, Chem. Zentr. 1895, i. 
1105). It has sp.gr. 1-4584 at 0° (Bruhl, Ber. 
1895, 28, 2854). It forms hydrates H20j,Hj0, 
Hj02,2H20 (Wolffenstein, I.e. 3311). 

When heated to the boiling-point of water it 
decomposes with explosive violence into oxygen 
and water, but when the peroxide or its solu- 
tions are quite pure it is not so readily decom- 
posed by heat ; the vapours of Wdrogen 
peroxide are said to be qidte stable (Wolffenstein, 
Ber. 1894, 27, 3307 ; Nernst, Zeitsch. physikal. 
Chem. 1904, 46, 720). 

The liquid evaporates slowly in vaeu6 
without the residue undergoing any change 

prepared. Crystals of the EMnO^ should be placedin a 
Woulfl's bottle containing 1 : 9 smphurio acid, and the 
3 p.c. solution of H2O2 allowed to drop regularly into 
the solution from a suitable reservoir. 



(Thenard). It bleaches organic colouring matters, 
but not BO quickly as chlorine; when brought in 
contact with the skin it forms a white blister, 
which, after a time, produces an irritable, 
itching sensation (Wolffenstein, I.e.). 

One volume of the concentrated solution 
yields at 14° and 760 mm. pressure, 476 
volumes of oxygen, the theoretical amount being 
501-8 volumes (Thenard). The compound is 
most stable in dilute aqueous solution; when 
the solution is subjected to great cold, part of 
the water freezes out. 

Hydrogen peroxide is a remarkalle oxidising 
agent. It converts arsenious into -arsenic acid, 
and sulphurous acid into sulphuric acid ; lead 
and other sulphides into the corresponding 
sulphate ; manganese monoxide into dioxide 
and monoxides of iron and cobalt into the 
sesquioxides. The monoxides of barium, stron- 
tium, and calcium are converted by it into their 
respective peroxides. The concentrated solution 
of hydrogen peroxide acts with violence on 
selenium, arsenic, molybdenum, and chromium, 
converting them at once into their oxides. 

It decomposes alkaline copper, silver, and 
bismuth nitrate solution w;th evolution of 
oxygen and formation of the metallic oxide, or 
in the last case the hydroxide (Berthelot, Compt. 
rend. 1901, 132, 897; Moser, Zeitsch. anorg. 
Chem. 1906, 50, 33 ; Gutbieu and Biinz. Chem. 
Zentr. 1909, i. 732). 

Hydrogen peroxide oxidises organic sulphides 
into sulphoxides (Gazdar and SmUes, Chem. Soc. 
Trans. 1908, 1833). It also reacts with benzene 
in presence of ferrous sulphate, forming phenol 
(Young, Chem. Soc. Proo. 1899, 131), and with 
a-diketones, and generally with substances 
possessing a quinonoid structure, and can there- 
fore be employed for oxidising phenolic substances 
like brazilein and aurin, without havingto protect 
the hydroxyl group by methylation (Perkin, 
Chem. Soc. Proc. 1907, 166). Hydrogen 
peroxide reacts with a number of opium alkaloids 
forming new crystalline bases (Freund and 
Speyer, Pharm. Zeit. 1907, 52, 116). According 
to Schaer (Arch. Pharm. 1910, 248, 458), it may 
be use's as a test for other alkaloids. A few 
milligrams of the alkaloid to be tested are 
added to a cooled mixture of the peroxide and 
sulphuric acid. Quinine gives a lemon or 
canary yellow colour; berberlne a cherry red; 
hydrastine a chocolate ; emetine a dark 
orange, and nicotine a blood-red colour. 

In presence of ferrous sulphate hydrogen 
peroxide also reacts with a number of sugars, 
forming osones (Cross, Bevan, and Smith, Chem. 
Soc. Trans. 1898, 403; Morell and Bellars, ibid. 
1905, 280 ; Chem. Soc. Proc;. 1902, 65 ; Chem. 
News, 1904, 90, 158). It also reacts with other 
organic compounds (Cross, Bevan, and Heiberg, 
Chem. Soc. Proc. 1899, 130 ; Harden, t6»d. 168 ; 
Wolffenstein, Ber. 1895, 28, 1469 ; Bevan and 
Heiberg ibid. 1900, 33, 2016; aover and 
Haughton, Amer. Chem. J. 1904, 32, 43). 

Pure hydrogen peroxide reacts with potas- 
sium oyanidp thus : 

KCN+H,02=KCN0-fHs0 
KCN0-f2Hj0=K(NH4)C0,. 
Potassium formate and ammonia are also pro- 
duced, but if the peroxide contains acid, then 
oxamide is formed (Masson, Chem. Soc. Trans. 
1907, 1449). 



HYDROGEN PEROXIDE. 



71 



With potaasJum persulphate it reacts thus : 

HjO,+KjS,08=2KHSOi4-Oa 

an unstable intermediate compound is also 
formed (Friend, Chem. Soo. Trans. 1906, 1092). 

With sodium thiosulphate it gives the 
reaction ; 

Na2S208+4HjOa=Na2S30,+2NaOH+3HjO 
Na2SsO,+2NaOH+iH,Oj=2NaaS04+5HjO 
(WiUstatter, Ber. 1903, 36, 1831). 

In presence of certain solid substances, es- 
pecially when finely divided, hydrogen peroxide 
undergoes violent decomposition, the substances 
themselves remaining unchanged (FiUippi, Chem. 
Zentr. 1907, ii. 1890 ; Antropoff, Zeitsch. 
physikal. Chem. 1908, 62, 513 j Bredig Willde, 
Biochem. Zeitsch. 1908, ii. 67). This is the case 
with carbon, many metals, and oxides, and 
iodine (Walton, Zeitsch. physikal. Chem. 1904, 
47, 185 ; Abel, Zeitsch. Elektrochem. 1908, 14, 
689). Gold, platinum, and particularly silver, 
act most violently a,nd evolve great heat. The 
presence of acids retards this decomposition, 
whilst the presence of alkalis facilitates it. 

This decomposition is still more readily 
brought about by those metals when in the 
colloidal state (Bredig and Reinders, Chem. 
Zentr. 1901, ii. 87; Bredig, Zeitsch. physikal. 
Chem. 1899, 31, 258 ; ibid. 1901, 37, 323 ; ibid. 
38, 122; Price and Denning, ibid. 1903, 46, 
89; Brossa, ibid. 1909, 66, 162; Spear, J. 
Amer. Chem. Soc. 1908, 30, 195 ; see also Kastel 
and Loevenhart, Amer. Chem. J. 1903, 29, 563 ; 
Liebermann, Ber. 1904, 37, 1519; Bredig, ibid. 
798 ; Poppada, Gazz. chim. • ital. 1907, 37, 
ii. 172). 

Hydrogen peroxide is also decomposed by 
catalases, a class of organic ferments which are 
widely distributed in the animal and vegetable 
kingdoms (Senter, Proo. Roy. Soo. 1904, 74, 201 ; 
Wender, Chem. Zeit. 1904, 28, 300, 322 ; Euler, 
Chem. Zentr. 1905, i. 941 ; Bach, Ber. 1904, 37, 
3785 ; ibid. 1905, 38, 1878 ; Laer, Bull. Soo. 
chim. Belg. 1906, 19, 337; J. Inst. Brewing, 
1906, 12, 313 ; Rywosch,-Centr. Bakt. Par. 1907, 
i. 44, 295). 

Hydrogen peroxide also acts as a deoxidising 
agent ; thus silver oxide when brought in contact 
with it causes a mutual decomposition of the 
two compounds Ag20+H202=H20+02+Ag2, 
an atom of oxygen is liberated from each com- 
pound, and a molecule of free oxygen is thus 
obtained. A similar reaction occurs when hy- 
. drogen peroxide and ozone are brought together, 
H20a+03=,H20+202 (Mulder, Rec. trav. chim. 
1903, 22, 388; Baeyer and ViUiger, Ber. 1902, 
34, 749 ; 2769 ; Indis, Chem. Soo. Trans. 1903, 
1013). 

- Hydrogen peroxida is reduced by manganese 
dioxide and peroxide of lead in presence of an 
acid, H202+Mn02=Mn0+02-f HjO. 

Alkaline mercury salts are reduced to the 
metallic state by hydrogen peroxide (Kolk, 
Chem. Zeit. 1901, 25, 21). Direct sunlight 
accelerates the decomposition of hydrogen 
peroxide. The effect of hydrogen peroxide on 
a photographic plate is similar to that of light, 
and is probably due to the hydrogen peroxide 
vapour itself, and not to a radiation from it 
(Russell, J. Soc. Chem. Ind. 1899, 616 ; OtsuM, 
ibid. 1905, 576 ; Precht and Otsuki, ibid. 290 ; 
Dony-Hdnault, ibid. 1904, 138 ; Graetz,^ Chem. 



Zentr. 1904, ii. 1561 ; Dony-H6nault, ibid. 1906, 
ii. 203 ; Bull. Soc. chim. Belg. 1908, 22, 224 ; 
Soelaud, Ann. Physik. 1908, [iv.] 26, 899). 

Hydrogen peroxide forms molecular com- 
pounds with certain inorganic and organic salts 
in which it appeats to play the same part as 
water of crystallisation (Tanatar, Chem. Zeit. 

1901, 26 ; Rep. 326 ; J. Russ. Phys. Chem. Soc. 
1903, 40, 376 ; Staedel, I.e. ; Jones and Carroll, 
Amer. Chem. J. 1902, 28, 284 ; WiUstatter, Ber. 
1903, 36, 1828; De Eororand, Compt. rend. 

1902, 134, 601). 

An acidified solution of potassium dichro- 
mate in presence of hydrogen peroxide gives 
rise to an unstable combination of chromic acid 
and the dioxide ; this, on mixing with ether, can 
be extracted from the aqueous solution, impart- 
ing to it a beautiful and characteristic blue 
colour. 

A solution of guaiaciim mixed with a small 
amount of blood gives a blue colouration on 
addition of hydrogen peroxide. This is a deli- 
cate test for the compound, and serves also as a 
test for blood. 

Hydrogen peroxide gives a blue-green 
colouration with an alcoholic solution of guaiacol 
and sulphuric acid, and an intense yellow colour 
with a solution of quinine sulphate in concen- 
trated sulphuric acid (Denigfes, Pharm. J. 1909, 
July 31st). 

In the presence of hydrogen peroxide, 
chlorates, bromates, iodates, phosphates, sul- 
phates, and alkali hypohalites, also salts of 
organic acids, give a yellow-green colouration 
with 1 p.c. guaiacol solution. On addition, of 
hydrochloric or sulphuric acid the colour changes 
to red (Baudran, Compt. rend. 1906, 141, 891). 
Solutions of vanadio and titanic acids are turned 
brown or red by the peroxide and with a mixture 
of potassium chlorate and aniline in the presence 
of acid a violet colour is formed after a short 
time (Bach, Compt. rend. 1894, 119, 1218); if 
dimethylaniline is used instead ol aniline, a 
yellow colour is formed. By the la.tt6r reaction 
1 part of peroxide in 5,000,000 can be detected. 

When hydrogen peroxide is added to a solu- 
tion of potassium iodide, even in presence of 
ferrous sulphate or copper sulphate, iodine is set 
free, which may be shown by the colouration of 
starch. Hydrogen peroxide is the only com- 
pound known which can liberate iodine in pre- 
sence of ferrous sulphate (c/. Traube, Ber. 1884, 17, 
106?), 1 part in 25,000,000 oan thus be detected. 

A very delicate reagent for hydrogen per- 
oxide has been suggested by Charitschkofi 
(Chem. Zeit. 1910, 34, 60). It consists of the 
pinkish-red cobalt salts of the naphthenic acids 
obtained from the waste liquors from the refining 
of petroleum with alkali. A strip of filter paper 
is dipped into a petroleum solution of the 
cobalt salt, and, after drying, is moistened 
with the Uquid to be tested. If the peroxide is 
present the colour changes immediately to olive- 
green. Ozone does not give this reaction. 

For other tests see Denigis (BuU. Soo. chim. 
1890, 797) ; Aloy {ibid. 1902, 27, 734) ; Precht 
and Otsuki (Zeitsch. physikal. Chem. 1905, 52, 
236). 

TecJimcal applications. — ^Moistened lead sul- 
phide in contact with hydrogen peroxide is 
quickly oxidised to lead sulphate. This fact 
has led to the employment of hydrogen 



72 



HYDEOGEN PEROXIDE. 



peroxide as a picture restorer. The painting dark- 
ened by age or by exposure to air containing 
sulphuretted hydrogen, owing to the white lead 
employed as body colour being partially con- 
verted into lead sulphide, after careful treatment 
with an aqueous solution of the peroxide is 
found to be greatly improved in colour from the 
oxidation of the sulphide to the white sulphate. 

Dilute solutions of hydrogen peroxide mixed 
occasionally with nitric acid, are also used as 
' auricome,' ' golden hair water,' &q., for impart- 
ing a light colour to the hair (Sohrotter, Ber. 
1874, 7, 980; Lange, Dingl. poly. J. 1886, 
289, 196). 

It is also employed for removing the last 
traces of chlorine from vegetable fibres which 
have been bleached with the latter, and to remove 
the last traces of sulphur dioxide from bleached 
wool and silk. 

Hydrogen peroxide may be used for bleaching 
in many cases where other agents, such as 
bleaching powder, sulphurous acid, chlorine, 
would be injurious. It is particularly valuable 
for bleaching ostrich feathers, bones, ivory, silk, 
vi^ood, cotton, the teeth, &c. 

The advantages of using hydrogen peroxide 
as a bleaching agent, particularly for wool, are 
claimed to be the following : a purer white can 
be obtained ; the fibres are not tendered by it 
to the same extent as by the sulphur bleach ; the 
wool, after bleaching, does not turn yellow, does 
not emit an vmpleasant odour when in contact 
with perspiration, and purer tones and more even 
colours can be obtained on dyeing the bleached 
wool. It is also stated to be more convenient 
to use, more pleasant for the workpeople, and 
less corrosive on the machinery. With care, 
the process, moreover, need not be much more 
expensive than with the older bleaches, and it is 
now used very extensively and with good 
results, both in England and on the Continent 
(Wachtel, Farber-Zeit. 1900, 11, 268 ; Russell, 
Proc. Roy. ^c. 1899, 64, 409). 

In the case of wool the scoured article is first 
soaked thoroughly in a dilute solution of sodium 
silicate (2 lbs. to 10 gallons). After saturation 
the wool is wrung out and placed in the peroxide 
bath, which is prepared by adding 3J gallons of 
10 volume peroxide to 6^ gallons of water in 
which J lb; of sodium silicate has been dissolved. 
The wool is kept in the bath for about 24 hours 
(or a shorter or longer interval depending on the 
quality of ' the wool and on the whiteness 
desired) at 80°P. Occasionally the wool is 
turned over, and the solution tested whether 
it is alkaline, which it must be for satisfactory 
results. It is then pressed through a wringing 
machine and dried at a temperature of 15°-17°C., 
and preferably in the sunlight. When quite dry 
the wool is weU washed and redried (Fawsitt, 
J. Soo. Chem. Ind. 1902, 229; Luttringhaus, 
Farber-Zeit. 1901, 12, 328; Dommergue, Rev. 
Chim. Ind. 1896, 7, 73). 

With slight modifications this process is also 
applicable to cotton, straw and silk, but for the 
two last, the peroxide solution is made up of 
1 part 10 volumes peroxide to 2 of water, and for 
every 10 volumes of peroxide, 4 ozs. of sodium 
Bihoate is employed (Fawsitt, I.e. ; Koechlin, J. 
Soo. Chem. Ind. 1899, 1119). In the case of silk 
the bath may be made strongly alkaline with 
caustic soda from the beginning of the process. 1 



Bone and ivory are first cleansed by treat- 
ment with light petroleum, ammonia or other 
solvent ; they are then immersed in a bath con- 
taining 1 of 10 volumes peroxide to 2 of water 
made slightly alkaline witb ammonia. Feathers 
are bleached similarly, hut are washed after 
bleaching with a dilute solution of sulphuric acid. 

On a small scale lace can be bleached con- 
veniently in the following way : The material, 
after being moistened with water, is immersed 
in a solution of potassium permanganate for 
a few minutes. It is then rinsed and treated 
for about 10 minutes with a very dilute solu- 
tion of hydrogen peroxide, after which it is 
treated with acid to remove the manganous 
oxide formed in the previous operation (Thomas, 
J. Soc. Chem. Ind. 1900, 734). 

For bleaching delicate materials the hydrogen 
peroxide should not be too strong; a solution 
of 1 in 10 is strong enough, and a bleaching vat 
of this solution may be used for a long time 
if the strength be kept up by fresh additions 
of hydrogen peroxide. In bleaching dead hair, 
it is first digested for 12 hours in a solution of 
3 parts of ammonium carbonate in 100 of water 
at a temperature of 30°C., rinsed, then washed 
with soap and treated with ammonium, carbonate 
untE all fatty matter is removed. Thus prepared 
it is treated in a bath of hydrogen peroxide and 
water as in the first case. 

Hydrogen peroxide has been used for tanning 
leather, also to disinfect hides that have been 
long stored, and to preserve extracts of tanning 
materials (Gohring, J. Soc. Chem. Ind. 1890, 
84). It has also been recommended for use in 
photographic processes (Smith, J. 1873, 1131 ; 
Gros, D. R. PP. 147131; 153769; 158368; 
Otsuki, I.e. ; Liippo Cramer, Chem. Zeit. 1902, 
26, Rep. 292, 336 ; Ebert, ibid. 27, Rep. 152). 

Medicinal and surgiccd applications. — As an 
antiseptic and disinfectant it has the advantage 
of (1) being odourless; (2) yielding oxygen 
without leaving any residuum but pure water ; 
(3) absence of injurious influence on theorganism. 

The antiseptic properties of hydrogen 
peroxide solution were first brought into notice 
by Richardson in 1860. They were also studied 
by Kingzett, and subsequently by Paul Bert and 
Regnard (Compt. rend. 1882, 94, 1383), 

It is used in the treatment of syphilitic and 
scrofulous sores, alveolar abscesses, and purulent 
discharges. It is also of great value in cases of 
purulent discharge from the conjunctiva, and 
it is particularly efficient for destroying diphthe- 
ritic membranes. , 

Its behaviour is that of a powerful oxidising 
agent, but on healthy skin its action is slow. 
In contact with fistulous wounds or pus it 
is rapidly decomposed with effervescence, which 
continues till the wound is cleansed or the 
diseased secretion is destroyed (Kingzett, J. 
Soc. Chem. Ind. 1890, 3 ; Paneth, Chem. Zentr. 
1890, 174 ; Schmidt, ibid. 1906, U. 145 ; Jaubert,^ 
ibid. 1905, ii. 99). 

Hydrogen peroxide may be used to 
bleach discoloured teeth. In cases where the 
teeth are covered with coloured matter {Lichen 
dentalis, &c.) peroxide of hydrogen io conjunc- 
tion with finely levigated pumice-stone may 
be employed in place of water. A suitable 
liquid for cleansing the teeth and mouth is 
prepared by mixing 1 part of 3 p.o. peroxide 



HYDROLYSIS. 



73 



of hydrogen with 9 parts of water (Chem. News, 
45, 71 ; and Ch. Trade J. AprU 14, 1888). 

It has been proposed to use mixtures of 
hydrogen peroxide containing starch, cooked or 
in viscid solution, with anhydrous calcium 
sulphate as dentrifices, the starch preventing loss 
of oxygen from the oxide and the latter pre- 
serving the starch from putrefaction (Queissier, 
Fr. Pat. 381924, 1907; J. Soo. Chem. Ind. 
1908, 226). 

Hydrogen peroxide has the power of freeing 
water from living organisms, a property which 
has been utilised in brewing. It also destroys 
the acid and mould ferments in the wort. In 
stronger doses it destroys the alcoholic ferment 
and stops fermentation (G. Eeisenbichler, Chem. 
News, 66, 219; Miquel, Monit. Scient. 1884, [3] 
14, 170 ; Chodat and Bach, Ber. 1902, 35, 1276 ; 
Loew, Md. 2487 ; Bonjean, Compt. rend. 1905, 
140, 50 ; Lae^, J. Inst. Brewing, 1909, 16, 653). 

Altenhofer has recommended hydrogen per- 
oxide as a disinfectant for drinking water 
(Zentr. Bakteriol and Parasiteukde, 1890, 
129 ; Kuster, Chem. Zentr. 1889, i. 411 ; 1891, 
ii. 272 ; 1895, i. 948 ; but see also Gourmont, 
Nagier, and Rochaix, Compt. rend. 1910, 160, 
1453). 

Hydrogen peroxide is one of the chief con- 
stituents of ' sanitas,' which is a solution of the 
products of oxidation of terpentine oil in the 
presence of water and air (Kmgzett). 

It has been tried with success in the pre- 
servation of beer ; after a month the taste and 
aroma of the beer remained good (Weingartner, 
Bied. Zentr. 1884, 428). 

Hydrogen peroxide has been suggested as a 
useful and harmless preservative of milk (Jablin 
and Gounet, Ann. Chim. anal. 1901, 6, 129 ; J. 
Soc. Chem. Ind. 1902, 420; ibid. 1906, 1184; 
Fr. Pat. 366547 ; Amberg, J. Biol. Chem. New 
York, 1906, i. 219). 

To test milk for hydrogen peroxide, 10 drops 
of a 2 p.'c. alcoholic solution of benzidine and 
a few drops of acetic acid are added to 10 o.c. of 
the milk. If hydrogen peroxide is present a 
blue colouration appears. The peroxide can be 
detected in this way in other liquids if a little 
milk serum is added (Wilkinson and Peters, 
Zeitsoh. Nahr. Genussm. 1908, 16, 172, 515, 589 ; 
for other tests, see Feder, ibid. 15, 234 ; Arnold 
and Mentzel, ibid. 1903, 6, 305). 

Hydrogen peroxide is used in the laboratory 
in the valuation of bleaching-powder, the 
principle depending upon the fact that hypo- 
chlorites, -when mixed with hydrogen peroxide, 
instantly evolve all their oxygen, at the same 
time liberating the oxygen of the peroxide (J. 
Soo. Chem. Ind. 1887, 391). It is also employed 
in estimating the amount of active oxygen in 
potassium permanganate and in manganese 
dioxide (Schlossberg, Zeitsch. anal. Chem. 1902, 
41, 736 ; Carnot, Compt. rend. 1893, 116, 1295). 
The amount of sulphur in sulphides is also 
determined by first oxidising the sulphate and 
then proceeding as usual (6. Lunge, Ber. 18, 
1872 ; see also Baumann, Zeitsch. angew. Chem. 
1890, 72; Talbot and Moody, J. Soo. Chem. 
Ind. 1893, 780). 

Hydrogen peroxide has been employed in 
the separation of a number of metals from one 
another (Rose, Ber. 1894, 27, 2227 ; Lesinsky, 
ibid. 1893, 26, 1496, 2331, 2908 ; Jannasoh and 



Rottgen, Zeitsch. anorg. Chem. 1895, 8, 202; 
Friedheim and Bruhl, Zeitsch. anal. Chem. 1899, 
38, 681). Also for the separation of the halogens 
(Jannasch and Zimmermann, Ber. 1906, 39, 
196, 3656), and for separating vanadium from 
ores and slags (Fr. Pat. 367397 ; J. Soc. Chem. 
Ind. 1906, 72). 

Hydrogen peroxide has also been used as a 
solvent for Indian gum (BuU. Soo. Ind. Mulhouse, 
1894, 36), but its use in the estimation of the 
quantity of flour in a mixture of the latter with 
bran, is consider,ed to be untrustworthy by , 
Bremer (Zeitsch. Nahr. Genussm. 1906, 11, 
569). 

Hydrogen peroxide has been employed with 
success in determining the amount of sulphur in 
coal gas. The solution used for this purpose 
consists of the commercial product diluted to a 
1 p.c. solution. This solution is run into the 
Referees' ' apparatus,' through which the coal 
gas passes at a measurable rate, and the sul- 
phurous acid gas in it is oxidised to sulphuric 
acid S02-fHjj02=SOiH2. The amount of sul- 
phur is then determined by titration or precipi- 
tation (J. Soc. Chem. Ind. 1887, 286). 

Higher oxides of hydrogen. — ^The oxides 
HjG, and H,Og have been described (Bach, 
Ber. 1900, 33, 1506, 3111 ; ibid. 1902, 35, 158 ; 
Berthelot, Compt. rend. 1900, 131, 637), but it 
is doubtful whether they really exist (Armstrong, 
Chem. Soo. Proc. 1900, 134 ; Ramsay, Chem. Soo. 
Trans. 1901, 1324 ; see also Baeyer and ViUiger, 
1900, 33, 2488 ; Clover, Amer. Chem. J. 1903, 
24, 463 ; Bruhl, Chem. Zentr. 1896, i. 86 ; Nagel, 
Pharm. Zeit. 1898, 43, 556). Kastner (J. 1820, 
472) described a suboxide, but its existence has 
not been confirmed. 

HYDROGEN SULPHIDES v. Stophur. 

HYDROLITES v. Agate. 

HYDROLYSIS. Tbe term hydrolysis (or 
hydrolytic dissociation) is given (to a number of 
different chemical reactions, all of which consist 
in the addition of water to a complex, and the 
subsequent resolution of the product into 
simpler substances. 

Some of the best-known types of hydrolysis 
are those of metallic salts, esters, acid chlorides, 
amides, &c., or generally acyl derivatives, 
complex carbohydrates, and glucosides, and 
finally, polypeptides and proteins. 

1. Hydrolysis of salts. The hydrolysis of a 
salt by water may be represented by means of 
an equation of the type : 

KCN+H-OH t^ HCN-f-KOH. 
The reaction is a balanced one, and may be 
regarded as due to the incomplete neutralisation 
of the acid and base from which the salt is 
derived; in terms of the ionic theory the acid in 
question (HCN) does not yield sufficient hydrions 
to combine with the hydroxyl ions of an equiva- 
lent quantity of the strong base (KOH). When 
equivalent quantities of a strong acid and a 
strong base are brought together in aqueous 
solution complete neutralisation takes place, 
and & normal salt with a neutral reaction 
towards common indicators is formed. (Basis 
of methods of aoidimetry and alkalimetry.) In 
the cases of such salts appreciable hydrolysis ■ 
would not be expected even in dilute solution. 
The following are the common types of salts 
which are hydrolysed by water : (1) salts derived 



74 



HYDROLYSIS. 



from feeble acids and strong bases ; (2) salts 
from strong acids and feeble bases ; (3) salts from 
feeble acids and feeble bases. As examples of 
the first type we have potassium cyanide and 
sodium phosphate. 

KCN+H-OH ^ HCN+KOH 
NaaPOj+H-OH ^ Na^HPOj+NaOH 
and even 

NajHPOi+H-OH ^ NaHjPOi+NaOH 

Solutions oi such salts invariably have an 
alkaline reaction towards common indicators, 
e.g. litmus, phenolphthalein. The water may 
be regarded as a feeble acid, which, like any 
other feeble acid, liberates a certain amount of 
acid from the salt, with which it is brought into 
contact. In many cases acid salts are first 
formed, e.g. sodium phosphate, sodium carbon- 
ate, but free acid and free base may be liberated. 
The alkaline reaction of the solution can be 
accounted for by the fact that the feeble acid, 
or the acid salt formed, is ionised to a slight 
extent only, whereas with moderatdy dilute 
solutions the strong base is almost completely 
ionised, and thus there is a great excess of 
hydroxyl ions over hydrions. As examples of 
the second type we have ferric chloride and 
oupric sulphate, which are derived respectivdy 
from the feeble bases, ferric hydroxide and 
cuprio hydroxide. The aqueous solutions of 
such salts invariably give an acid reaction. 
The hydrolysis may be represented by means 
of the equations : 

Peaj+H-OH <^ Feaj-OH+Ha 
or even Fea,+3H-0H <^ Fe(OH)3+3Ha 
and CuS04+2H!-0H <^ OuCOHjj+HjSO,. 
With moderately concentrated solutions basic 
salts, e.g. FeQj-OH are almost certainly formed, 
and it is only in very dilute solution that the 
hydrolysis will proceed to the formation of the 
metallic hydroxide, and even when this is 
formed it is not precipitated, but remains in 
solution in the form of a colloid. A group of 
saJts which belongs to this type is that of the 
salts dervied from feeble organic bases such as 
aniline, and from the strong mineral acids, e.g. 

CeHs-NHja+H-OH ^ CeHj-NHj-OH+HCa 

Aniline Aniline 

hydrochloride. hydroxide.- 

^ CeH^NHs+HjO+Ha 
As examples of the third type we have ferric 
phosphate, aluminium carbonate and sulphide, 
and aniline acetate. The hydrolysis in the first 
case is readily shown by washing finely divided 
ferric phosphate with distilled water, when it 
is found that the filtrate is always distinctly 
acid,, owing to the free phosphoric acid which 
has been washed away by the water, and if the 
operation is continued nearly pure ferric 
hydroxide remains on the filter. In the case 
of the two aluminium salts, they are so readily 
hydrolysed that when brought into contact 
\nth water they yield the corresponding metallic 
hydroxide, and the free acids, carbonic acid and 
hydrogen sulphide, which escape and thus 
destroy the equilibrium. 

In the case of salt formation we may regard 
the water as capable of acting as either a feeble 
base or a feeble acid. When in contact with 
equivalents of a strong acid and a feeble base 



the water competes with the base for the acid, 
and hence neutralisation is not complete, or^ in 
other words, hydrolyis of the salt occurs and 
the feebler the base the greater the degree of 
hydrolysis. The mechanism of salt hydrolysis 
according to the ionic theory is as follows ; In 
aqueous solution the^ given salt, e.g. potassium 
cyanide is ionised in the ordinary manner into 

K and CN ions, but watei itself is ionised to a 

certain extent, HjO ^ H+OH, and as hydrogen 
cyanide is a very feeble acid, and therefore 
ionised to only a very slight extent in aqueous 

+ 
solution, there is a tendency for the H ions of 

the water to combine with the CN ions from the 
cyanide, yielding undissociated HON, the result is 

that the equilibrium HaO^H+OH is destroyed 

and more itiolecules of water are ionised, but 

this results in further combination between 

+ 

H and CN ions, and by this means an excess of 

OH over H ions is produced, and thus the alka- 
line reaction. The changes continue until 
ultimately an equilibrium is established between 

the KCN, CN, K, H, OH, HCN, and H^O 
present. The degree of hydrolysis, t.e. the 
fraction of the salt hydrolysed, cannot be 
determined by direct titration of the free acid or 
free base present in the solution ; the addition 
of standard acid to the solution of potassium 
cyanide would immediately destroy the equih- 
brium which previously existed, and more salt 
would be hydrolysed in order to restore the 
equilibrium, and the point of neutrality would 
not be reached until acid sufficient to decompose 
the salt completely had been added. The 
methods commonly adopted for determining the 
degree of hydrolysis are (c/. Farmer, B. A. Report 
1901, 240) : 1. JDetermination of the concentra- 
tion of the free acid or free alkali present in the 
solution of the salt by its catalytic effect on the 
hydrolysis of an aqueous solution of ethyl acetate 
or on the inversion of a solution of cane sugar, 
and then determining the amount of pure acid 
OB alkali required to produce the same effect 
(for acid, cf. Walker, Zeitsch. physikal. Chem. 
1889, 4, 319 ; for alkaU, cf. Shields, ibid. 1893, 
12, 167 ; also Bruuer, ibid. 1900, 32, 133 ; Ley, 
ibid. 1899, 30, 216 ; Walker and Aston, Chem. 
Soc. Trans. 1895, 67, 576). 2. Determination of 
the electrical conductivity of the solution (Walker, 
Zeitsch. physikal. Chem. 1889, 4, 333 ; Bredig, 
ibid. 1894, 13, 313 ; Denham, Chem. Soc. Trans. 
1908, 93, 4t). The molecular conductivity of a 
hydrolysed salt of the type aniline hydrochloride 
is made up of two quantities : (a) conductivity 
due to the non-hydrolysed ssilt ; (6) conductivity 
due to the free acid formed on hydrolysis — since 
the free base (aniline) is not an electrolyte. 
M = [l—x)Ui+xu^^,whsTe M = molecular con- 
ductivity, a:=degree of hydrolysis, «i=mole- 
onlar conductivity of non-hydrolysed salt. The 
various quantities in the equation with the 
exception of z can be determined and then x 
calculated. 3. By determining the partition 
coefficient (Farmer, Chem. Soc. Trans. 1901, 79, 
863). In the case of aniline hydrochloride the 
hyitolysis of the salt leads to the formation of 



HYDROLYSIS. 



78 



free aniline and hydrochloric acid, and the 
concentration of the free base is determin~ed by 
shaking the aqueous solution at a given tempera- 
ture with a known Tolmne of benzene, and find- 
ing the concentration of the aniline in the 
benzene layer. Since C^/C^ is always constant 
{Og=oonoentration of aniline in benzene and 
C^^=conoentration of aniline in water) for a 
given temperature the concentration of free 
aniline in the aqueous layer can be calculated 
directly, and thus the degree of hydrolysis 
determined. The assumption is made that the 
salt present does, not effect the partition co- 
efficient to an appreciable extent. 4. By the 
change in colour produced by a solution of the 
hydrochloride of an organic base on a solution 
of methyl orange of known concentration, and 
a comparison of this change with that produced 
by the addition of known quantities of hydro- 
chloric acid (Veley, Chem. Soc. Trans. 1908, 
93, 652, 2114, 2122 ; 1909, 95, 758 ; Trans. 
Far. Soc. 1808, 4, 19). 

Most of the methods give only rough approxi- 
mations (cy. Beveridge, . Proo. Roy. Soc. Edin. 
1909, 29, 648). A few of the results obtained 
are as follows : — 











Salt 


i 


■sSI 


Method 




S 








25° 


jao 




Glycine hydrochloride 


1900 


Hydrolysis of ester 


Acetoxime „ 


25 


3600 


» ' i» 


Urea „ 


25 


90-00 


» M 


Urea ,, 
Sodium cyanide 


60 


81-00 


Inversion of sugar 


25 


1-10 


Saponlfloation o( 
ester 


„ acetate 


25 


0-008 


„ carbonate , 


25 


817 


f( 11 


„ phenate 


25 


8-05 


f* )i 


Aniline hydrochloride 


60 


2-60 


Inversion of sugar 


,, ,, 


25 


1-50 


Conductivity 


Zinc chloride . 


100 


010 


Inversion of sugar 


Aluminium chloride . 


100 


6-10 


„ „ 


>t 1. • 


25 


0-50 


Conductivity 


Ferric chloride . 


40 


10-00 


Inversion of sugar 


Lead „ 


25 


0-50 


Conductivity 



The whole question becomes more compli- 
cated when the acid or base formed by hydrolysis 
is unstable and is transformed into an isomeride 
(pseudo-acid or pseudo-base). 

The influence of concentration on hydrolysis 
is given by Guldberg and Waage's law of mass 



a 



C^XC^ 



= constant. 



action. According to this 

where Cg represents the concentration (molar) 
of the non-hydrolysed salt, 0^ that of the 
acid formed by hydrolysis, and C^ that of the 
base.' If originally 1 gram mol. of salt was 
dissolved in v litres of solution and x gram 
mols. were hydrolysed, then 



1—z jx z_ 



:constant, or 



- Hl-x) 



= constant. 



It is obvious that as v increases, i.e. as the 
concentration is diminished, x, i.e. the degree 
of hydrolysis, must increase in order to keep the 
whole expression constant. 

The relationships are not quite the same 



in the case of a salt derived from a feeble base 
and a feeble acid, e.g. aniline acetate. 
C.Hj-NH.-O-CO-CHs+HjO 

^ CHj-NHa-OH+CHj-CO-OH. 
If the reaction is represented as taking place 
between the ions of the salt and the water, 
and the salt is practically completely ionised, 
and the base and acid not appreciably, then 
^o»t''-'An/*\'^B==''°°^**°*> '^here CQ^j=concen- 
tration of the cation and C, = concentration 



CLt/C^-CB 



=constant, or ( 



"Salf 

jab 



^constant 



Cat ^An 

\v) / v'v 

where s, a, h are the gram mols. respectively of 
salt, acid, and base in v litres of solution. But 
this expression is independent of v, and hence 
dilution does not affect the degree of hydrolysis. 

Another factor which affects the degree of 
hydrolysis is the addition to the solution of 
one of the products of hydrolysis, e.g. free acid 
or free base. Thus the hydrolysis of aniline 
hydrochloride in aqueous solution can be stopped 
completely by the addition of hydrochloric acid 
or of aniline. This follows again directly from 
the equation Cg/C^-C3=Constant. If C^^, i.e. the 
concentration of the acid is increased it is neces- 
sary, in order that the whole expression may 
remain constant, that either C^ should diminish 
or Cg increase or both, and the only way in 
which this can be affected is by a diminution in 
the degree of hydrolysis. 

The velocity of salt hydrolysis has been 
determined in a few cases, e.g. ferric chloride 
(Goodwin, Zeitsch. physikal. Chem. 1896, 21, 
I ) ; potassium ruthenium chloride KjRuClj 
(Lind and Bliss, J. Amer. Chem. Soc. 1909, 31, 
868). 

A type of hydrolysis analogous to salt 
hydrolysis is that of the chlorides of certain 
non-metals, e.g. PCl3+3HaO=3HCl+P(OH)a. 
This reaction proceeds to completion in the 
presence of an excess of water, and, as a rule, 
the chlorides of non-metals are hydrolysed more 
readily than those of metals. Nitrogen tri- 
chloride and carbon tetrachloride are, however, 
stable in the presence of water and many 
metallic chlorides derived from feeble electro- 
positive metals are appreciably hydrolysed, e.g. 
Feaj,Bia3, &c. 

2. Hydiolysis of esters. The hydrolysis of 
^n ester may be brought about by water alone, 
by solutions of neutral metallic salts, by aqueous 
solutions of strong alkalis or acids, by water in 
the presence of finely divided solids, such as 
charcoal, and also by means of enzymes. 

The reaction with water may be represented 
by an equation of the type : 
CH.-CO-OCaHj+H-OH 

^CHs-CO-OH-fCaHsOH 

The reaction is the reverse of esterification, and 
is hence a balanced bimolecular reaction ; in 
dilute solutions, however, the mass of the water 
may be regarded as remaining constant, and 
the reaction becomes practically non-reversible. 
The course of the reaction can be followed by 
estimating the amount of free acid in the solu- 
tion after given intervals of time ; this is accom- 
plished by removing an aliquot part of the solu- 
tion at the given time and titrating the free 



76 



HYDROLYSIS. 



acid by means of standard alkali solution. In 
most cases it is necessary to use a feeble alkali 
for titration, e.g. ammonium hydroxide using 
litmus as indicator, as nearly all esters which 
are hydrolysed appreciably by water are decom- 
posed very readily by strong alkalis, and it 
becomes impossible to tell the end point of the 
titration when sodium op barium hydroxide 
solutions are used. Comparatively few esters 
are hydrolysed to any appreciable extent by 
water at the ordinary temperature, the few 
that have been investigated are esters derived 
from comparatively strong acids, e.g. ethyl 
nitrate, ethyl formate, ethyl trichloroacetate, 
and ethyl pyruvate. In these cases the velocity 
of the reaction does not correspond with that 
of a simple unimolecular reaction, the values for 
K calculated by means of the usual equation 
K=l/< log a/a—x, increase as t increases, and 
the probable reason is that the acid formed 
during the hydrolysis reacts catalytically on the 
reaction (see under hydrolysis by acids). Hydro- 
lysis of natural glyceryl esters by means of 
superheated steam is used as a commercial 
method for the production of stearic acid for the 
manufacture of candles. 

The hydrolysis of esters by means of dilute 
mineral acids is slow and readily lends itself to 
study as a time reaction. The velocity is 
directly proportional to the concentration of 
the mineral acid, i.e. probably to the hydrions 
which act as a catalyst, and the reaction may 
be represented by the differential equation 



dx/dt= 



'^■'^Eater''^H20"*^H' 



In dilute solution, and most esters are some- 
what sparingly soluble in water, 0„ g can be 
regarded as not changing, and C^ is also constant, 
since the catalyst is not used up during the 
reaction. The process thus becomes a typical 
unimolecular reaction, and the velocity constant 
can be determined with the aid of the usual 
formula K=I/< log, a/a—x. 

The concentration of the organic acid at 
any given time is obtained by titrating a portion 
of the solution with standard barium hydroxide 
solution and phenolphthalein (unless the ester 
is derived from a strong acid when ammonia 
and litmus are used) and subtracting from the 
total alkali used the amount required by the 
mineral acid. The foUbwing relative values 
have been obtained at 25°, using 0-1 N-hydro- 
chloric acid as catalyst working with the 
methyl, ethyl, and propyl esters of acetic, 
propionic, and butyric acids : 

K methyl ester : K ethyl ester=0'97 
and K ethyl ester : K propyl ester=l-01. 

K acetate ester : K propionate ester=l-07 
K propionate ester : K butyrate ester= 1-75 
K butyrate ester : K vaJerate ester=2-93. 
From these values it is clear that in the hydro- 
lysis of an ester R-CO-OR' by means of a strong 
mineral acid the aoyl group R-CO has a much 
greater influence than the alkyl group R' on 
the velocity of hydrolysis (Hemptinne, Zeitsch. 
physikal. Chem. 1894, 13, 562). Lowenherz 
(Md. 1894, 15, 389) working at a temperature 
of 40° found that ethyl formate is hydrolysed 
much more readily than ethyl acetate (ratio 
20 : 1) ; that methyl and ethyl monaohloroace- 
tates are hydrolysed at much the same rates, 
ratio 1-01 : 1, that the ratio K ethyl acetate :K 



ethyl monoohloroacetate=l-7 and that K ethyl 
dichloroacetate : K ethyl monoohloroacetate 
=1'6, and that ethyl benzoate is hydrolysed 
extremely slowly. 

The majority of chemists are of opinion that 
the process of hydrolysis consists first of all in 
the formation of an additive compound between 

/OH 
the ester and the water, e.g. R-C^OH {cp. 

\OEt 
esteriflcation), and the subsequent breaking up 
of this into acid and alcohol. The manner in 
which the complex dissociates, e.g. into water 
and ester, or into alcohol and acid, will depend 
largely. on the relative amounts of water and 
alcohol present. A view put forward by 
Stieglitz, and supported by many chemists 
(cp. Acree and Jolmson, Amer. Chem. J. 1907, 
38, 335), is that the ester, being a feeble base, 
combines with the strong mineral acid used as 
catalyst, forming a salt, e.g. R-C02Et,HCl, only 
small amounts of such salts would be formed, 
as the base is an extremely feeble one. The 
salt would be ionised in the usual manner into 

+ 
d ions and complex cations R-COjEt.H. It is 
these complex cations which then react with the 
water and undergo hydrolysis 

+ • + 

R-C02Et,H+HjO=R-COjH+EtOH-fH 
and the assumption has to be made that the 
hydrolysis of the complex cations proceeds more 
rapidly than the hydrolysis of the ester molecules. 
The view that it is the complex cation and not 
the unionised salt (ester hydrochloride) which 
reacts, with the water is supported by the fact 
that the rate of hydrolysis is directly propor- 
tional to the concentration of the mineral acid, 
i.e. to the concentration of the hydrion and not 
to the square of the concentration of the hydrion. 

The hydrolysis of an ester by means of an 
alkali hydroxide can be represented by an 
equation of the type : 

^■<^<OEt+^OH=RO^g^j-fEtOH. 

The reaction is non-reverSible, as the alkali salt 
cannot react directly with the alcohol, and as 
both ester and alkali are used up as the hydrolysis 
proceeds the reaction should be bimolecidar. 
Hydrolysis by alkalis proceeds more rapidly than 
that by mineral acids \cp. Van Dikjen, Reo. trav. 
chim. 1895, 14, 106), and is the common method 
used in the laboratory. The ester is boiled for 
some time with an excess of sodium (or potas- 
sium) hydroxide solution in a flask fitted with a 
reflux condenser. If the ester is an oil only 
sparingly soluble in water, the completion of the 
reaction is denoted by the disappearance of the 
oily layer, unless the alcohol formed is also 
insoluble in water. If, however, the ester 
itself is soluble in water, but has a characteristic 
odour, the disappearance of the odour indicates 
complete hydrolysis. In order to separate the 
acid and alcohol formed, the mixture is (a) 
boiled, when the alcohol passes over together 
with water, provided the alcohol is a compara- 
tively simple monohydric one; (6) extracted 
with ether if the alcohol is complex and is not 
readily volatUe. To obtain the acid the alkaline 
solute left after treatment (a) or (6) is acidified 
with hydrochloric acid, when the organic acid 
is directly precipitated if it is sparingly soluble 



HYDROLYSIS. 



T7 



in water, or can be extracted with ether if 
soluble in water. 

An alcoholic solution of potassium hydroxide 
is sometimes used for hydrolysing purposes, 
especially when the ester is practioaJly insoluble 
in water. 

The decomposition of esters by alkaKne 
hydroxide solutions is the basis for the usual 
methods for the manufacture of hard and soft 
soaps (see Soap; SAPONiriCATion), and hence a 
common name for the process is ' eaponifica- 
tion' The common fats are glyceryl esters c(t 
monobasic acids of high molecular weight, more 
especially of palmitic, stearic, and oleic acids, 
and on saponification yield the trihydric alcohol 
glycerol and the sodium or potassium salts of 
the acids, e.g. 
C3H5(O-C0-0i,H35),+3NaOH 

=Cl3H,(OH),+3C„H,5-COONa. 

Reicher (Annalen, 1885, 228, 257) was one of 
the first to determine the velocity of saponifica- 
tion under varying conditions. When the alkali 
and ester are not used in equivalent quantities 
the differential equatipn is of the type 

d^/dt='K.(a-x)t})-x) 
where a and h are the original concentrations, 
and a—x and h—x the concentrations at the 
time t. When integrated this gives an equation 



K=- 



rlog. 



h(a—x) 



tifl—l) ^ a(b—x) 
for calculating K. The concentration of the 
alkali at any given time is determined by 
titration with standard acid and the concentra- 
tion of the ester calculated from that of the 
alkali, as with an ester of the type of ethyl 
acetate, the disappearance of each gram molecide 
of alkali entails the disappearance of a gram 
molecule of ester (c/. Warder, Amer. Chem. J. 
1882, 3, 340 ; Ber. 1881, 14, 1311). The velocity 
constant K can be calculated by means of the 
equation 



K= 



O^t "'^' 0(0.- 



Coe) 



0«) 



where 0, C/, and 0^5 denote the concentration 
of the alkali just after mixing, the concentration 
after time t and the concentration after complete 
hydrolysis (24^48 hours). 

Reicher's experiments were carried out at 
9-4°, and show that the velocity is practically 
the same whether sodium, potassium, or calcium 
hydroxide is used as saponifying agent. With 
strontium or barium hydroxide the velocity 
constants are somewhat smaller and with a 
feeble alkali, such as aiomonium hydroxide, the 
value for K is much less, e.g. 

K^aOH = K^H.OH=200:l. 
The results obtained by using different esters 
show that the alkyl group R' in the ester 

R-O^Q-g, influences the rate of hydrolysis to 

a greater extent than it does when mineral acids 
are used for hydrolysing; thus the values for 
K using sodium hydroxide at 9-4° are : methyl 
acetate 3-49, ethyl acetate 2-31, propyl acetate 
1'92, jsobutyl acetate 1-62, and isoamyl acetate 
1-64. The influence of the acyl group R-CO is 
also marked, as shown by the following values 
for K at 14 '4°, using sodium hydroxide and 
ethyl eeters : acetate 3*2, propionate 2-8, 



butyrate 1'7, jsobutyrate 1-73, jsovalerate 0-62, 
and benzoate 0-83. Later experiments by Sud- 
borough and Feilmann (Chem. Soo. Proc. 1897, 
13, 243) prove that the introduction of methyl 
groups into the ethyl acetate molecule retards 
hydrolysis by means of alcoholic potassium 
hydroxide, whereas the introduction of chlorine 
atoms facilitates the decomposition. The in- 
vestigations of Gyr (Ber. 1908, 41, 4308) sho^ 
that two or three phenyl groups in the ethyl 
acetate molecule also retard hydrolysis, whereas 
the ethyl ester of pheuylacetio acid is hydrolysed 
more readily than ethyl acetate itself. The 
results obtained by Hjelt (Ber. 1896, 29, 1864) 
with substituted derivatives of ethyl malonate 
also show that the introduction of an alkyl 
group into the ethyl malonate molecule retards 
hydrolysis, and that when two such groups are 
present the effect is still more noticeable. The ' 
influence of the strength of the acid from which 
the ester is derived also appears to be a deter- 
mining factor. The investigations of KeUas 
(Zeitsch. physikal. Ohem. 1897, 24, 243). on the 
hydrolysis of ethyl esters of substituted benzoic 
acids show that the esters of many substituted 
benzoic acids are hydrolysed by alcoholic potash 
more readily than ethyl benzoate itself. This 
appears to be true of all esters derived from 
acids much stronger than benzoic acid, e.g. the 
bromo-, chloro-, and nitro-benzoic acids, but 
does not hold good when the esters are derived 
from acids with small dissociation constants, 
e.g. the toluio acids. KeUas's results also show 
that when the rates of hydrolysis of a group of 
three isomeric esters are compared the ortho- 
compounds are invariably hydrolysed more 
slowly than the isomeric, meta-, and para- com- 
pounds, even when the ortho- acid is a much 
stronger acid than the isomers. 

Findlay and Turner (Chem. Soc. Trans. 1905, 
87, 747) and Findlay and Hickmans {ibid. 1909, 
93, 1004) show that an o-hydroxyl group 
increases the readiness with which the ester is 
hydrolysed by alkalis. The ratio K ethyl 
glycoUate : K ethyl acetate=ll-5 ; and K ethyl 
lactate : K ethyl propionate=ll'9, and K methyl 
mandelate : K methyl phenylacetate =6-7. The 
introduction of a phenyl group in the 
a-position does not necessarily increase the 
rate of hydrolysis. The ratio K ethyl phenyl- 
acetate : K ethyl acetate =l-9, but K ethyl 
mandelate : K ethyl glycolIate=0-88. It is 
shown that there is no direct proportionality 
between the affinity constant of the acid and 
the saponification constant of its ester, although 
in any given series of compounds the two con- 
stants follow the same order. The results ob- 
tained by different authorities point to the 
general conclusion that two factors at least 
determine the rate of hydrolysis of ethyl esters 
by alkalis or acids, (a) The complexity of the 
acyl group, especially as regards the presence 
of substituents in close psoximity to the carbonyl 
group, e.g. in the o-position in aliphatic, the 
ortho- position in aromatic, and probably the 
cis- position in unsaturated esters. (6) The 
strength of the acid from which the ester is 
derived. When mineral acids are used as 
hydrolysing agents the rate of hydrolysis appears 
to be determined largely by the first factor, 
although the second factor also has an effect, 
as shown by the fact that ethyl trichloroacetate 



78 



HYDBOLYSIS. 



J3 hydrolysed more readUy than the diohloro- 
acetate. When alkalis are used and also probably 
when water alone is used, the second factor has 
a much more marked effect than when acids 
are used; the effect ia so marked in certain eases 
that the influence of the first factor is almost 
completely obscured, e.g. with the esters of 
the chloroacetic acids, of the o-hydroxy acids 
and of nitro substituted benzoic acids. 

The generalisation drawn by V. Meyer 
(Ber. 1895, 28, 1263; cp. Wegscheider, ibid. 
2636) viz. that there is a simple relationship 
between the rate of hydrolysis of an ester by 
alkahs and its rate of formation by the catalytic 
method of esterification does not hold. It is 
highly probable that there may be a relation- 
ship between the rate of esterification of an acid 
by the direct method and the rate of saponifica- 
tion of the ester, and also a relationship between 
the rate of hydrolysis of the ester by acids and 
the rate of esterification by the catalytic method. 
No relationship between the rate .of saponifica- 
tion or by hydrolysis by acids and the con- 
stitution of the aJkyl group R' in the ester 

R'C<^Qjji, can be deduced as the data available 
are not sufficiently numerous. 

Since sodium, potassium, and calcium 
hydroxides as saponifying agents have practi- 
cally the same effect when solutions of equivalent 
strengths are used, the conclusion has been 
drawn that the hydrolysis is due to the hydroxyl 
ions present. The reaction cannot be a simple 
addition of the alkali to the ester followed by 
the elimination of alcohol, as then the reaction 
with calcium hydroxide would be termolecular 
2B.-C02Et+Ca(OH)a=(B-C02)2Ca+2EtOH 
whereas it can be shown to be bimolecular. 

It is possible that the reaction consists in 
the addition of water (not alkali) to the ester 
and the subsequent resolution of this complex 
into acid and alcohoL The alkali in this case 
would act first as a catalyst, and secondly 
as a base for neutralising the acid formed. 
According to Acree (Amer. Chem. J. 1907, 38, 
344) the ester can function as a feeble acid and 
form small amounts of salts with the alkali. 



acid, the two stages proceed at very different 

CH2-0Me(C0jEt)^ 
rates, the'normal ester ' 



I^CMe,, 



e.g. 



CH,-C<gR, KOH ^ CHjC^OH -f K 

and it is the complex anion which reacts with the 
water yielding the anion of the acid and alcohol 

CHj-C^OH = CH,-C<X+ROH 

Esters of difcasie acids. J. Meyer (Zeitsch. 
physikal. Chem. 1909, 66, 81, and 67, 257) by 
the study of the hydrolysis of esters of dibasic 
acids (tartaric, succinic, and camphoric) with 
hydrochloric acid as catalyst, has been able to 
prove that the reaction proceeds in two distinct 
stages ; (o) normal ester+water— >acid ester 
-f alcohol; (i) acid ester -f water— >acid+ alcohol. 
With the ethyl esters of symmetrical dibasic 
acids, e.g. tartaric and succinic, the whole 
reaction appears to be unimoleCular as the 
velocity coiistant for the first stage is almost 
exactly double that for the second stage, and 
the whole is pseudo- unimolecular. In the case of 
ethyl camphorate, the ester of an unsymmetrical 



CHi,-CH(COjEt' 
is rapidly hydrolysed to the acid ester, 
CH,-CMe(COiiEt)\ 
I J;CMe,, 

CHa-CH(COjH)-^^ 
but this latter is fairly stable, and the method is 
a convenient one for the preparation-of the acid 
ester. For different esters of the same acid the 
influence of the alcoholic group on the rate of 
esterification is scarcely noticeable, whereas the 
constitution of the acyl group has a marked 
effect. Experiments carried out with the same 
esters using alkali hydroxide as hydrolysing 
agent show that here also the reaction proceeds 
in two distinct stages, but the relationship 
between the velocity constants of the two is 
not so simple as when hydrochloric acid is used. 
With ethyl malonate the first stage proceeds 
about 100 times as quickly as the second, but 
with ethyl succinate the ratio is about 10 : 1, 
and in neither case can the whole process be 
represented as a simple bimolecular reaction. 
With the esters derived from symmetrical di- 
hydric alcohols, e.g. glycol diacetate C2H4(OAc)2, 
although the saponification proceeds in two 
distinct stages the velocity constants of the 
two stages bear a simple relationship to one 
another, e.g. 2 : 1, and hence the whole appears 
to be a bimolecular reaction. The same holds 
good for the hydrolysis of glyceryl triacetate, 
where the three distinct stages proceed at' the 
relative rates 3:2:1. 

_ Esters of sulphonic acids. Esters of sulphonic 
acids can also be hydrolysed by water, mineral 
acids, or alkalis, and since most- of the sulphonic 
acids are very strong acids, their esters are 
hydrolysed quite readily by water alone. The 
esters are also converted into the corresponding 
acids when heated with alcohol (Krafft and Roos, 
Ber. 1892, 25, 2225 ; Kastle and Murrill, Amer. 
Chem. J. 1895, 17, 290), a reaction in which an 
alkyl ether is also formed 

RSOj-OEt+EtOH=RSOs-OH+EtaO 
This decomposition proceeds slowly at the 
ordinary temperature, and is brought about 
more readily by methyl than by ethyl alcohol. 

Kastle, Murrill, and Erazer (Amer. Chem. 
J. 1897, 19, 894) have shown that 0-1 iV-solutions 
of sulphuric and acetic acids have no effect on 
the hydrolysis of esters of sulphonic acids by 
water.- Hydrochloric and hydrobromic acids, 
on the other hand, have an apparent retarding 
effect, but this is due to the fact that the 
halogen hydracids can react with the ester 
according to the equation : 

RSOj-OEt+Ha ^ R-SOa-OH-f-Eta 
a reaction which does not affect the total acidity 
of the solution. A more detailed investigation 
has proved that this second reaction proceeds 
more rapidly and to a greater extent than the 
hydrolysis of the ester by water. The hydrolysis 
of a siilphonio ester by means of a large excess 
of water or alcohol in acetone solution gives 
concordant values f6r K when the equation for 
a monomoletJUIar reaction is used. Alkalis are 
much more efficient hydrolysing agents than 
water for sulphonic esters; this may be due to 
the alkali acting independently of the water or 



HYDROLYSIS. 



79 



to the alkali oatalytically afiecting the hydrolysis 
by water. The oonstants at 25° for methyl 
benzenesulphonate, using water and J^-potassium 
hydroxide solution, are 1 ; 90 (Wegsoheidei and 
Furcht, Monatsh. 1902, 23, 1903). When the 
neutral ester of a mixed carboxyUo sulphonic 
acid is hydrolysed, e.g. OEt-SOj-OuHj-COaEt, 
the -SOa-OEt group is hydrolysed much more 
readily than the -COjEt group, and an acid 
ester of the type OH-S02-CjH4-C02Et is formed. 

Esters can also be hydrolysed by water with 
finely divided metals as catalysts, e.g. Neilson 
(Amer. J. physiol. 1903, 10, 191) has shown 
that platinum blacic accelerates the hydrolysis 
of ethyl butyrate by water. The reaction is, 
however, very slow, and increases with the 
amount of platinum present. The maximum 
effect is obtained at 60°, and the activity of 
the catalyst is readily destroyed by various 
' poisons. ' The reaction is reversible as platinum 
black can also accelerate the esterification of 
butyric acid in ethyl alcoholic solution. 

Sabatier and Maihle (Compt. rend. 1911, 162, 
494) have shown that titanium dioxide is a good 
catalyst for the conversion of acids and alcohols 
into esters. The method adopted is to allow 
a mixture of molecular quantities of the vapours 
of the two compounds to pass over a column of 
the dioxide kept at 280°-300°. The yield of 
ester is much the same as in Eerthdot and 
Menschutkin's experiments, but the process is 
extremely rapid. The reaction is reversible, and 
using equivalent quantities of acid and alcohol 
an approximately 70 p.c. yield of ester was 
obtained in most cases examined. A similar 
method may also be used for hydrolysis of 
esters. It consists in allowing a mixture of the 
vapour of the ester with an excess of steam to 
pass over the titanium dioxide at 280°-300°. 

Similar results can be obtained with thorium 
oxide as catalyst provided aromatic acids of the 
type of benzoic are used (ibid. 368). 

Certain neutral metallic salts also act cata- 
lytically on the hydrolysis of esters by water 
(Kellog, J. Amer. Chem. Soo. 1909, 31, 403, 886). 
The salts which have been investigated are 
potassium chloride, bromide, and iodide. The 
catalytic effects are comparatively small when 
compared with those of strong acids, the chloride 
has the greatest effect and the iodide the least, 
and when the concentration of the salt reaches 
a certain value the catalytic effect is negative. 
No simple explanation of the results can be 
given. 

Hydrolysis ol halogen derivatives. The 
hydrolysis of chloroaoetic acid CHaCl-COjH and 
of its sodium salt to glyooUio acid OH-CH j-COjH 
has been studied. With water at high tempera- 
tures the reaction is unimoleculai and non- 
reversible, and when salts of the acid are used 
the velocity appears to be independent of the 
base with which the chloroacetic acid is com- 
bined. The velocity coefficients of N-, 0-3 N-, 
and 0-1 ^-solutions of salts of monochloro- and 
monobromoacetic acids are inversely propor- 
tional to the affinity constants of the two acids. 
The rate diminishes with dilution and reaches 
a minimum at about 0-1 iV, and from that point 
to v=1000 the velocity of decomposition is 
practically constant (Kastle and Keiser, Amer. 
Chem. J. 1893, 16, 471). 

Senter (Chem. Soc. Trans. 1907, 91, 460j has 



shown that N solutions of hydrochloric acid 
and neutral salts have but little effect, and that 
the hydrolysis of the monochloroacetic acid is 
directly proportional to the concentration of 
the acid within wide limits. At 102° it is 
shown that the reaction is strictly unimoleculai 
in dilute solution, but that slight deviations are 
met with in more concentrated solutions. The 
reaction is presumably between uniom'sed water 
and unionised acid, and when the sodium salt is 
used the reactiwi is between unionised water 
and both unionised salt and the anion. When 
sodium hydroxide is used for hydrolysis at 102° 
the reaction is bimoleoular in dilute solutions, 
although deviations are met with in more 
concentrated solution, and the reaction with the 
alkali proceeds some 10 times as fast as with 
water alone. For comparison of rates of 
various o-bromo acids and sodium salts, cp. 
Chem. Soc. Trans. 1909, 95, 1835. The 
velocity reaction between the sodium salt of the 
acid and water is appreciably increased by the 
introduction of methyl and ethyl groups into 
the acid molecule, whereas the reaction between 
th^ sodium salt and sodium hydroxide is re- 
tarded by the presence of alkyl substituents. 

The esters of imxTio acids can be hydrolysed 
in two different ways : 

(1) R-C<^f,+H,0 ~> R-C^gji,+NH. 

(2) KC^OR' "^ R-CiN+R'-OH 

The former reaction is enormously accelerated 
by acids and the latter by alkalis. According to 
SteigUtz (Amer. Chem. J. 1908, 39, 29, 166) the 
former reaction consists in the hycirolysis of the 

■I- 
oomplex cation (R-C{:NH)'OR',H), and the latter 

in the decomposition of the anion R'C(: N)-OR'. 
The effect of alkalis is much more pronounced 
than that of acids. When water alone is used it 
is the non-ionised ester which is decomposed. 

3. Hydrolysis of acyl derivatives. The chlo- 
rides, amides, anilides, and anhydrides of organic 
acids can be hydrolysed in much the same 
manner as esters, e.g. 
R-CO-Cl-fHOH=RCOOH-f HCl ; 

R-C0-NHPh-fK-0H=R-C0-0K+NH2Ph. 
As a rule the derivatives of aliphatic acids are 
hydrolysed more readily than those derived 
from aromatic acids, e.g. acetamide more readily 
than benzamide. The hydrolysis is usually 
effected by boiling with alkali hydroxide, but 
the presence of ortho- substituents in deriva- 
tives of benzoic acid retards hydrolysis to an 
appreciable extent (V. Meyer, Ber. 1894, 27, 
2163 ; Sudborough, Chem. Soc. Trans. 1894, 65, 
1030; 1895, 67, 587; 1897, 71, 229; Reed, 
Amer. Chem. J. 1899, 21, 281). When two such 
substituents are present the amide cannot be 
hydrolysed by boiling with potassium hydroxide 
solution, but the hydrolysis may be accomplished 
by heating with concentrated hydrochloric or 
hydrobromic acid under pressure in sealed tubes. 
One of the most convenient methods for con- 
verting a diortho- substituted benzonitrile into 
the corresponding acid is to hydrolyse to 
the amide R-CN-fHjO=R-CO-2SrHj by 
heating at 120°-130° with 90 p.c. sulphuric 
acid, and when cold to replace the amino group 
by hydroxyl by the addition of sodium nitrite 



80 



HYDROLYSIS. 



solution (Bouveavilt, Bull, Soc. ohim. 1892, [Hi.] 
9, 368 ; - Sudborough, Chem. Soo. Trans. 1895. 
67, 602). 

The hydrolysis of aoetamide by hydrochloric 
Boid has been studied by Aoree and Nirdlinger 
(Amer. Chem. J. 1907, 38, 489). The amount of 
hydrolysis after given intervals of time was 
determined by introducing known volumes of 
the reaction mixture into a Lunge nitrometer 
containing sodium hypobromite solution and 
measuring the nitrogen evolved. Their results 
show that at 65° the reaction is practically 
unimolecular when dilute solutions are used, but 
that the values for K tend to increase with the 
time, probably owing to a slight catalytic effect 
of the ammonium chloride formed on hydrolysis. 
These chemists conclude that the hydrolysis of 
an acid amide by mineral acids is analogous to 
the hydrolysis of an ester or the inversion of 
cane sugar by acids, and that the first stage 
consists in the formation of a small amount of 
salt between the acid and the amide, the final 
stage consisting in the hydrolysis of the complex 
cation derived from the salt. 

CHa-CO-NHj+H+a+HjO 

^ CHaCONHa+HjO+ci 

-> CH,-COaH+NH.+d 

Croker and Lowe (Chem. Soc. Trans. 1907, 
91, 593, 952) have studied the hydrolysis of 4he 
amides of the simple aliphatic acids with hydro- 
chloric acid, and also with sodium hydroxide 
solution, _ using the electrical conductivity 
method in order to determine the amount of 
amide hydrolysed. The order of the amides 
when hydroohlorio acid is used is formamide, 
propionamide, acetamide, isobutyramide, capro- 
namide, butyramide, and valeramide ; but with 
sodium_ hydroxide the order is formamide, 
acetamide, propionamide, oapronamide, butyra- 
mide, jTObutyiamide, and valeramide, in both 
cases formamide is- the amide most readily 
hydrolysed, and in every case the hydrolysis 
with alkali proceeds more rapidly than that with 
hydrochloric acid under similar conditions. 

E. Kscher (Ber. 1898, 31, 3266) has pointed 
out that uric acid and similar cyclic nitrogen 
derivatives are less readily hydrolysed by 
dilute alkalis than their alkylated derivates, e.g. 
1:3: 9-trimethyl uric acid. Similarly the amide 
and methyl ester of the methyl ether of salicylic 
acid are more readily hy(h:olysed than the 
corresponding derivatives of sahcylio acid itself, 
and in all such cases the compounds most 
resistant to the hydrolysing agent are those 
which can form metallic salts with the alkalis. 

These facts support Stieglitz's view that in 
hydrolysis by alkalis a salt of the alkali and 
amide (or ester) is formed and that the complex 
anion of this salt undergoes hydrolysis. When 
the amide or ester contains a replaceable 
hydrogen atom, salt formation of a different 
type occurs, and the characteristic complex 
anion is not formed. 

Most compounds of the type of alkylated 
acid amides, e.g. compounds containing the 

grouping ■ C-C:^q , can be hydrolysed. 
Thus hippurio acid (benzoylglycine) 
C,Hb-CONHCH,-CO,H 



is hydrolysed to benzoic acid and glycine hydro- 
chloride when boiled with concentrated hydro- 
chloric acid. The hydrolysis of naturallj 
occurring protein derivatives, by means of acidi 
or alkalis consists in the addition of water tc 
such groups and the subsequent resolution intc 
simpler cleavage products, ultimately into amino 
acids (see PiiOTBiifS). (For hydrolysis oi 
sulphonic acids, cp. Crafts, BuH. Soc. chim. 1907, 
[iv.] 1, 917.) 

4. Hydrolysis of di- and poly-saccharoses. Aa 
a rule compounds of the ether type, i.e. com- 
pounds containing two alkyl or substituted alkyl 
groups attached to oxygen,- are not readily 
hydrolysed when boiled with alkali or acid 
solutions. 

All the carbohydrates of the di- or poly- 
saccharose type take up water when warmed 
with dilute mineral acid and are resolved into 
mono-saccharoses. The best known examples 
are : 
sucrose (cane sugar) -|- water 

=glucose (dextrose)+fructDse (laevulose) 
malt sugar+water=dextrose 
lactose (milk 8ugar)-(-water 

=dextrose-f galactose. 

All these reactions can be represented by the 
equation : 

C,AjO„-fHjO=CeH,,Oe+C,H,A- 
Starch is also hydrolysed by dilute mineral 
acids yielding as final product dextrose : 

(C.Hi„05)ji+«(HjO)=«(C,H,aO,). 
The hydrolysis of cane sugar (sucrose) by 
means of dilute mineral acid has been examined 
in detail ; it is usually referred to as the inver- 
sion of sucrose, as the optical rotatory power 
changes from -(-to — during the reaction. The 
investigations of Wilhelmy (Pogg. Ann. 1850, 
81, 413, 499) proved that in dilute solution the 
amount of sugar inverted is proportional to the 
amount present, or, in other words, the reaction 
is unimolecular. The method of determining 
the concentration of the sucrose at any given 
time is based on polarimetrio readings, li the 
original rotation of the sucrose solution be 
+a;°, and after complete inversion be —y°, then 
the total change is a+y". If after an interval 
of time t the rotatory power of the solution is 
+z°, then the fraction of sucrose which has 

undergone mversion is -^-- , and the velocity 

constant can be determined by substituting the 
values for t, 0„ and C, in the equation 

K=l/nog.O./0, 
where C, represents the concentration of the 
sucrose at the .beginning and can be expressed 
by x+y, 0, represents the concentration at 
time t, and is equal to x—z. The velocity of 
inversion is directly proportional to the con- 
centration of the hydrochloric acid, and increases 
with rise in temperature. J. Meyer (Zeitsoh. 
physikal. Chem. 1908, 62, 69) states that the 
reaction between sucrose and dilute mineral acid 
is not a simple unimolecular reaction, but is 
complicated by the mutarotation of the glucose 
and fructose. ■ 

Hudson (J. Amer. Chem. Soc. 1908, 30, 1166), 
on the other hand, claims that the reaction is 
tpically unimolecular, and that the question 
of mutarotation does not arise, as both the 

a-£rluCOSe and a-fnip>.nnn firaf. tnvwnaA ,. — 3 



HYDROLYSIS. 



81 



mutarotation immediately in the presence of 
the acid giving the usual rotatory values for 
invert sugar. Even in the earlier readings 
deviations from the unimolecular reaction are 
not encountered. 

The hydrolysis of other di-saccharosea, and 
even of gluoosides by dilute mineral acids, also 
follows Wilhelmy's Law, but the relative rates 
are very different; the following values have 
been obtained for Jf-sulphuric acid at 20° : 
lactose 1, maltose 1-27, sucroSfe 1240; or again 
o-methylgluooside 100, and ;3-methyIgluooside 
179. The hydrolysis of carbohydrates by 
means of dilute mineral acids is the basis of 
certain commercial methods for the manufacture 
of glucose. Large quantities of this carbo- 
hydrate are manufactured by boiling starch 
{e.g, potato or maize starch) with dilute sulphuric 
acid, removing the acid by precipitating as 
calcium sulphate and evaporating the clear 
solution under reduced pressure. 

Neutral salt action. The investigations of 
Ostwald (J. pr. Chem. 1883, [ii.] 28, 460), Spohr 
{ibid. 1886, [ii.] 33, 265), and Arrhenius (Zeitsoh. 
physikal. Chem. 1889, 4, 234; 1899, 31, 207) 
prove that the addition of a substance which is 
largely ionised in aqueous mlution accelerates 
the hydrolysis of esters or of carbohydrates by 
aqueous solutions of strong acids. This has 
been proved by the addition of metallic chlo- 
rides to mixtures in which hydrogen chloride 
ia the catalyst, the addition of bromides to 
hydrogen bromide, and of nitrates to nitric acid. 
The majority of chlorides have much the same 
effect if readily ionised, whereas a salt such as 
mercuric chloride, which is only partially 
ionised, has a much feebler action. Non- 
electrolytes, such as methyl and ethyl alcohols 
have but little effect on the hydrolytic activity of 
hydrogen ions. The neutral salt action has 
been shown to be independent of the con- 
centration of the compound hydrolysed, and 
is stated to be proportionately greater the 
more dilute the acid solution, but Lunden 
(Med. Nobel Institut. 1910, 2) disputes this 
statement. 

CaldweU (Eroc. Roy. Soc. 1906, A, 78, 272), 
working with weight normal solutiojps, shows 
that the presence of metallic chlorides increases 
the catalytic activity of hydrogen chloride on 
the inversion of cane sugar, and that calcium 
chloride has the most pronounced effect. Similar 
effects on the activity of nitric acid are produced 
by nitrates (Whymper, ibid. 1907, A, 79, 
676). Salts also tend to increase the activity 
of hydrogen chloride when used as a catalyst 
in the hydrolysis of methyl acetate (Armstrong 
and Watson, ibid. 1907, A, 79, 679), but their 
effect is not so marked as in the case of the 
inversion of sucrose (cp. Armstrong, ibid. 1908, 
A, 81, 90 ; Armstrong and Crothers, ibid. 102). 
According to Armstrong and Caldwell the salts act 
by removing part of the water in the form of 
definite hydrated compound, and in this manner 
increase the ccmcentration of the reacting sub- 
stance. Senter (Chem. Soc. Trans. 1907, 91, 462) 
is of opinion that this view cannot be correct, 
as the relative neutral salt action of different 
salts is not that of their ordinary degree of 
hydration (c/. chlorides and nitrates), and as in 
equivalent solutions the effect is practically 
independent of the nature of the salt (cp. Jones, 

Vol. in.— r. 



Zeitsoh. physikal. Chem. 1906, 55, 355, 429). 
A further argument used by Senter is that where- 
as rise of temperature affects hydration to 
an appreciable extent, alteration of temperature 
has but little effect on neutral salt action. It 
is concluded that probably the earlier sugges- 
tion of Arrhenius is correct, namely, that the 
ions of the neutral salt have some action on 
the hydrions or hydroiyl ions of the catalyst. 

Reed (Amer. Chem, J. 1899, 21, 342) states 
that neutral salts retard the hydrolysis of acid 
amides by alkalis ; and Arrhenius (Zeitsoh. 
physikal. Chem. 1887, 1, 110) and Spohr (ibid. 
1888, 2, 1194) claim that the same effect is pro- 
duced by salt^ on the rate of hydrolysis of esters 
by alkalis. Senter, on the other hand {I.e. 473), 
shows that they accelerate the hydrolysis of 
sodium chloroaoetate by sodium hydroxide. 
Since neutral salts have no effect on the decom- 
position of sodium chloroaoetate by water, it 
is claimed that the effect of the salts cannot be 
due to their action on the reacting substance 
(the chloroaoetate), and probably is due to theii 
action on the hydroxyl ions (c/. Zeitsch. physikal. 
Chem. 1910, 70, 617). 

6. Hydrolysis by enzymes. Many of the 
hydrolytic processes induced by aqueous solu- 
tions of acids 01 alkalis can also be brought about 
by certain complex organic substances found in 
animal and plant tissues. Such substances are 
termed unorganised ferments or enzymes ; they 
act not merely as catalysts in processes of hydro- 
lysis, but certain of them induce processes of 
oxidation — ^the oxidases — and others can effect 
complex decompositions as exemplified by the 
decomposition of glucose into ethyl alcohol and 
carbon dioxide under the influence of zymase. 
I'he enzymes are somewhat unstable, nitro- 
genous, organic compounds of colloidal nature, 
but not necessarily proteins ; they act as 
catalysts, in the majority of cases as positive, 
but in a few as negative catalysts. The catalytic 
nature is shown by the fact that the rate of 
reaction is directly proportional to the con- 
centration of the catalyst, but that the total 
decomposition is the same whatever the amount 
of catalyst used, provided sufficient time is 
allowed, and provided the enzyme does not 
undergo decomposition owing to secondary 
reactions. One of the _most characteristic 
proofs of their catalytic nature is that due to 
Henri, who showed that when sugar was added 
after given intervals of time to a solution in 
which cane sugar was undergoing hydrolysis by 
invertase, the added sugar in each case began 
to be inverted by the enzyme at a rate irrespec- 
tive of the amount already decomposed. Unlike 
most organic ferments the enzymes are sensitive 
to high temperatures; thus when heated to just 
below 100° their activity is completely destroyed ; 
they are, however, resistant towards certain 
antiseptics which destroy protoplasm and kill 
fermenting organisms. A colloidal solution of 
an enzyme can often be prepared free from living 
organisms by treatment with a mild antiseptic, 
e.g. toluene, and filtration through a porous clay 
filter. Strong antiseptics such as formaldehyde 
are to be avoided, as they tend to destroy the 
enzyme also. -A study of enzyme action is often 
complicated by the fact that it is impossible to 
isolate, in a state of purity, the particular enzyme 
required, and it may be accompanied by another 



82 



HYDROLYSIS, 



enzyme capable of causing the destruction 
(autolysis) of the first, and thus bringing the 
reaction to an end long before all the substrate 
is decomposed. , ■■ i . 

The name given to a particular hydrolysing 
enzyme usually mdicates the substance it is 
capable of hydrdysing and in all oases the 
termination ase is used. Thus maltase is the 
enzyme which hydrolyses maltose, amylase the 
enzyme which hydrolyses starch ; but in some 
cases older names which were in use before this 
scheme was adopted, are still retained, e.g. 
sucrase, the enzyme which inverts sucrose (cane 
sujar), is BtiU called invertase or even invertin, 
the common digestive enzymes are termed 
trypsin and pepsin. The substance which is 
decomposed by the enzyme is usually termed 
the substrate. 

Although the processes of hydrolysis by acids 
and by enzymes are frequently compared it 
should be borne in mind that the rate at which 
a given substance is hydrolysed by the two 
difierent types of catalysts is frequently quite 
different, e.g. sucrose is hydrolysed by invertase 
much more readily than by a JT'-solution of 
hydroohloric aoid; in fact, with a concentrated 
solution of invertase at 0° the inversion is 
practically instantaneous. It is not essential 
that the products obtained by the two processes 
' should be identical. Thus in the case of the 
- inversion of cane sugar by invertase the products 
are o-glucose and o-fructose, whereas when 
mineral acids are used the products are equili- 
brium mixtures of a- and /S-glucose and o- and 
/3-fructose, as the a-glucose and the a-fruotose 
undergo immediate mutarotation in the presence 
of the mineral acid. Another example of a 
similar type is met with in the tri-sacoharose, 
raffinose ; when hydrolysed by acids this yields 
galactose, fructose, and glucose, the same sugar 
with raffinase yields meUbiose and fructose, and 
with emulsin it yields galactose and sucrose. 
Similarly natural products of protein character 
yield comparativdy simple amino acids when 
hydrolysed with acids or alkalis, whereas with 
enzymes more complex intermediate products 
are formed. 

An important point of difierence between 
hydrolysis by means of acids or alkalis and 
hydrcdysis under the influence of enzymes is 
that any particular enzyme has a very restricted 
use as a catalyst or the action of enzymes is 
essentially selective. Thus lipase can hydrolyse 
esters and not carbohydrates; maltase can 
hydrolyse maltose but not sucrose. That a 
slight difEerence in the configuration of two 
isomeric compounds is sufficient to affect their 
reactivities with a particular enzyme is shown in 
the case of the two stereoisomeric o-methyl- 
gluoosides. (For further details, see art. Fbk- 
MMNTATION.) Further examples are met with 
among the numerous polypeptides prepared 
within recent years {cp. Fischer and Bergell, 
Ber. 1903, 36, 2592; 1904, 37, 3103; Fischer 
and Abderhalden, Zeitsch. physiol, Chem, 1905, 
46,52; 1907,61,264). . , . 

The behaviour of some of the natural ana 
artificial glucosides {see GLtrcosroES) towards the 
two enzymes maltase and emulsin has been 
made use of in determining their configurations. 
Thus maltose, which is hydrolysed by maltase 
biit not by emulsin, is regarded as an anhydride of 



o-glucose having a configuration similar to that 
of the a-methylglucoside ; most of the natural 
glucosides, on the other hand, are hydrolysed 
by emulsin, but not by maltase, and therefore 
are probably analogous to 3-methylgluooside. 
As a rule a natural gluooside is accompanied in 
the plant tissue by the enzyme which is able to 
hydrolyse it. The commonest glucosidoolastic 
enzymes, t.e. enzymes capable of hydrolysing 
glucosides are emulsin (J8-glucase), myrosin, 
which hydrolyses sulphur glucosides, rhamnase, 
and tannase. 

The products formed by the hydrolysis of 
naturally occurring compounds by enzymes are 
various; thus the natural glucosides can give 
rise to sugars, alcohols, phenols, aldehydes, 
acids, mustard oils, antwacene derivatives, 
indigo, &c. 

It has been proved in many cases that a 
specific enzyme can act not merely as a hydrolys- 
ing, but also asa synthesising agent. The process 
of liydrolysis is thus, in certain cases, a balanced 
reaction, but the eoiuilibrium is mainly in the 
direction of analysis and not synthesis. The 
synthesising activity of an enzyme was first 
demonstrated by Croft Hill (Chem. Soo. Trans. 
1898, 73, 634; 1903, 83, 578) in the case of 
maltase. The greater portion of the maltose is 
hydrolysed by the enzyme to glucose, but a 
certain proportion of di-sacoharose is always 
present. 

Emulsin and lipase have also been shown , 
to possess s3Tithesising properties; in the 
latter case natural fats nave been synthesised 
by the action of lipases on mixtures of glyc'ferol 
and the higher fatty acids in the absence of a 
large excess of water. The Ijpatic enzymes 
present in certain seeds are made use of on a 
commercial scale for the preparation of fatty 
acids from natural fats (cp. Welter, Zeitsch. 
angew. Chem. 1911, 24, 38S; Pottevin, BuU. 
Soc. chim. 1906, [iii.] 35, 693). For details of the 
synthetic functions of enzymes, see art. Feb- 

MBNTATION. 

In some of these balanced actions between 
carbohydrates or esters and enzymes it has been 
shown that the equilibrium mixture is the same, 
whether mineral acid or enzyme is used, e.g. 
Visser's experiments using invertase and emulsin ; 
in other cases, however, the equilibrium mixture 
with the enzyme is quite different from that 
obtained when an acid is used, e.g. Dietz's 
experiments with lipase and i«o-amyl »-butyrate 
(Zeitsch. physiol. Chem. 1907, 52, 279). 

A considerable amount of work has been 
done on the velocities of different reactions in 
which enz3rmes play 'a part. Henri (Lois 
general de Taction des diastases, 1903) and others 
claim that the rate of inversion of suerose by 
invertase, unlike that by mineral acids, does not 
agree with the unimolecular formula. The 
investigations of O'Sullivan and Tompson 
(Chem. Soo. Trans. 1890, 57, 834) and of Hudson 
(J. Amer. Chem. Soo. 1908, 30, 1160, 1664; 
1909, 31, 655) prove oonclusivdy that the 
unimolecular formula holds for any given 
solution, if the birotation of the a-glucose and 
a-fruotose first formed is taken into considera- 
tion. The complications attending the mutaro- 
tation of the glucose and fructose can be avoided 
by adding a small amount of alkali, e.g. 10 o.c. 
of 0-4 ^-sodium carbonate solution fov each 



HYDROLYSIS. 



•«3 



100 0.0. of Bugar solution, a short time before 
the polarimetiio reading is taken.- The alkali 
stops the hydrolysis and rapidly brings about 
equilibrium between the a- and ;3-gIucoses and 
a- and J3-fruotoses, so that the normal rotatory 
power of invert sugar is given. Hudson's 
results olearly prove-that the a-modifications of 
glucose and fractose are first formed, and that 
Uiese are stable in the presence of enzyme, but 
rapidly undergo inutarotation in the presence of 
a Uttle alkali. Hudson's experiments also show 
that a trace of hydrochloric acid, e.g. 0-0006 N, 
accelerates the action of the invertase to an 
appreciable extent. 

The decomposition of the oane sugar is 
directly proportional to the concentration of the 
enyzme, and in very dilute solutions (under 
6 p.c.) is also proportional to the concentration 
of the sugar, but with more concentrated solu- 
tions it is not even approximately proportional, 
but decreases and becomes^ practically zero in 
the strongest solutions. According to O'Sullivan 
and Tompson, and to Hudson, the diminution 
in the velocity in concentrated solutions is due 
principally to the viscosity of the medium; it 
may also be partly due to the formation of a 
definite compound between the sugar and 
enzyme. According to A. J. Brown (Chem. 
Soc. Trans. 1902, 81, 373) a given quantity of 
invertase decomposes a nearly constant weight 
of sugar in unit time (t.e. the decomposition is 
independent of the sugar concentration), pro- 
vided the solution is moderately concentrated ; 
but after an appreciable amountj of sugar is 
decomposed the further inversion is directly 
proportional to the concentration of the sugar. 
This change of velocity from a linear to a logar- 
ithmic period is in harmony with the view that 
the,suga7 unites with the enzyme, and that it is 
the additive compound which is hydrolysed, and 
that the enzyme thus liberated immediately 
combines with a further amount of sugar. 
C'p. the hydrolysis of milk sugar by enzymes 
(B. P. Armstrong, Proc. Roy. Soc. 1904, 73, 
600). 

The reaction between salicin and water in 
the presence of emulsin is also a unimolecular 
reaction (Hudson and Paine, J. Amer. Chem. 
Soc. 1909, 31, 1242), provided alkali is added to 
bring about mutarotation of the /3-glucose, 
which is the primary product ~ ^ 

CxjHi80,-l-H20=C.H,jOa+C,H80a 

Sallcyl alcohol. 

The reaction between lipase and isoamyl 
butyrate or between the same enzyme and 
tsoamyl alcohol and n-butyric acid in the presence 
of a large excess of alcohol is a normal unimole- 
cular reaction, although it proceeds in a hetero- 
geneous medium. Dietz concludes that the 
reaction takes place in the solid phase, and that 
the difiusion of the ester or acid into the colloidal 
enzyme takes place so rapidly when compared 
with the velocity of reaction that the rates of 
diffusion do not affect the determination of the 
velocity of the reaction. 

The hydrolysis of ethyl butyrate by lipase 
(Pierce, J, Amer. Chem. Soc. 1910, 32, 1617) 
points to the formation of an additive compound 
of the ester and enzyme. In many other cases 
the velocity relationships are not so simple. In 
some of these the reaction is retarded after a 
certain time owing to the product or products 



formed combining with the enzyme, or to 
negative autocatalysis, or to the gradual de- 
struction of the enzyme. 

In the reaction between pepsin and albumen 
the amount of albumen transformed in given 
time by different amounts of pepsin is propor- 
tional to the square root of the pepsin concen- 
trations. The same relationship holds good 
with regard to trypsin and albumen, and is due 
to the fact that the velocity is inversely propor- 
tional to the amount of substance transformed, 
and this points to the formation of a definite 
compound between the enzyme and one of the 
products. 

Most decompositions by enzymes are charac- 
terised by a high temperature coefficient when 
compared with catalytic reactions in which acid 
or alkali is used. In the latter case the coeffi- 
cient is about 2-3 for a rise of 10° ; with emulsin, 
however, the coefficient is 7-14 for a rise from 
60° to 70°, with trypsin 6-3 for a rise from 
20° to 30° ; but like most colloidal catalysts 
enzymes exhibit an optimum temperature, at 
which the activity is greatest, and then falls 
again with further rise of temperature. This 
may be due to the coagulating effects which a 
moderately high temperature usually has on 
the majority of colloids. 

In certain cases it has been foimd possible 
to obtain by dialysis from a given enzyme two 
portions, a dialysate and a residue; neither 
portion alone is active, but the hydrolytia 
activity is restored when the dialysate is added 
to the dialysed residue. This residue is de- 
composed when boiled with water, and is the 
enzyme proper, whereas the dialysate is not 
decomposed when boiled and contains the co- 
enzyme (see art. Fbembntation). In the case 
of jjver lipases it has been proved that both 
enzyme and co-enzyme are essential for the 
hydrolysis of esters, and it has also been proved! 
that the co-enzyme is a metallio salt of tauro- 
choUo- acid. In living tissues a number of 
complex substances are present which are 
capable of interfering with the specific action 
of an enzyme. These are termed anti-enzymes ; 
some are normally present in tissues, others 
appear to be formed when an enzyme is injected 
into the tissue. 

A view generally held with regard to the 
mechanism of enzyme reaction is that com- 
pounds perhaps of the type of ' absorption com- 
pounds' (Bayliss) are formed between the 
enzyme and substrate, and that the absorbed 
material then reacts with water (see art. 
FliBMENlATiON). The fact that a specific 
enzyme "can hydrolyse only certain particular 
substrates is in harmony with this view, as 
it is known that chemical constitution plays 
an important part in absorption phenomena 
(Zung, Arch, inter. Physiol. 1907, 6, 245; 
Hedin, Bio-Chem. J. 1907, 2, 112; Aoree, J. 
Amer. Chem. Soc. 1908, 30; 1755; cp. also 
Freundllch, Zeitsch. physikal. Chem. 1907, 57, 
385). 

6. Alcoholysis. Reactions in which alcohols 
play much the same part as water in hydrolysis 
are usually grouped together under the n^me 
alcoholysis. The reaction with methyl alcohol 
is termed ' meihanolyaia,' and that with ethyl 
< ethanolysis.' 

The ethanolysis of an acid amide in the 



84. 



HYDROLYSIS. 



presence of a mineral acid is analogous to 
the hydiolysis of the amide by dilute mineral 
acids as shown by the two equations : 

B-C^^ +H-OH=RC^OH+N^» 

^■^NH,+H'0^*=^"^0Et+NH3- 

The latter reaction has been studied in detail 
by Reed (Amer. Chem. J. 1909, 41, 483). The 
reaction is bimolecular as the catalyst is gradu- 
ally neutralised by the ammonia formed in the 
reaction, and proceeds at an easily measurable" 
rate at 60° in the case of benzamide. A 
comparison of the values of K for 
J3- and m-nitrobenzamide. shows that this is 
1*16, a value practically identical with the ratio 
for the hydrolysis of the two amides. The ratio 
of the constants for benzamide and m-nitro- 
benzamide varies considerably with the concen- 
tration of the hydrogen chloride. The presence 
of small amounts of water on the rate of alcoholy- 
sis is also marked, just as in the case of the 
esterification of an acid, and similarly ortho- 
substituents appear to have inhibiting effects. 
The general conclusion drawn is that the 
mechanism of alcoholysis is analogous to that of 
hydrolysis, and consists in the formation of 
salts between. the amide and the mineral acid 
and the reaction of the complex cation with the 
alcohoL 

Anothei common type of alcoholysis met 
with is the conversion of an ester of a given acid 
into another ester of the same acid by means of 
an alcohol, e.g. : 

RCO-OEtH-MeOH ^ RCOOMe+EtOH. 
This change does not take place readily except 
in the presence of a catalyst, the most efBcieut 
being sodium alkyl oxide (Purdie, Chem. Soc. 
Trans. 1886, 47, 862 ; 1887, 51, 627 ; 1888, 63, 
391; aaisen, Ber. 1887, 20, 646), hydrogen 
chloride (Patterson and Dickinson, Chem. Soc. 
Trans. 1901, 79, 280), sodium hydroxide (Hen- 
riques, Zeitsch. angew. Chem. 1898, 338; 
Ffannl, Monatsh. 1910, 31, 301 ; Kommenos, 
ihid. 1910, 31, 111, 687 ; 1911, 32, 77 ; Kremann, 
ibid. 1905, 26, 783 ; 1908, 29, 23) or ammonia 
(Leuchs and Theodorescu, Ber. 1910, 43, 1239). 
As a rule only a small amount of the catalyst 
need be used, but with the esters of aromatic 
acids saturation with hydrogen chloride is 
necessary. The reaction appears to be rever- 
sible, as it is possible to transform an ethyl into 
a methyl and convfersely a methyl into an ethyl 
ester. The reaction is not limited to metlfyl and 
ethyl esters, but can be applied to more complex 
esters, such as benzyl and phenyl, and also to 
glyceryl esters (cp. Haller, Compt. rend. 1906, 
143, 667; 1908, 146, 269; Fanto and Stritar, 
Monatsh. 1908, 29, 299), and is a most convenient 
laboratory method for the conversion of a given 
ester into another ester derived from the same 
acid. The esters of the great majority of ali- 
phatic and aromatic acids react in this manner, 
but Sudborough and Edwards have shown that 
when the esters are derived from diortho-sub- 
stituted benzoic acids the transformation cannot 
be affected by using either sodium alkyl oxide or 
saturating with hydrogen chloride and boiling 
for some time. Even when several substituents 
are present transformation Occurs, provided the 
ortho- positions are free. This indicates that the 



transformation of esters under the influence of 
hydrogen chloride is analogous to the esterifica- 
tion of an acid by the same catalyst {see Esteei- 
fication). 

Similar transformations can be brought.about 
in the case of the alkyl ethers of carbonium 

/CH:CH 
bases, e,o. CeH.C | (Decker, J. pr. 

^NR-CH-OEt 
Chem. 1890, [ii.] 45, 182), and of the oxygen 
ethers of substituted thiocarbamides, t.g. 
OEt-OHj-NH-CS-NHPh 

->OMe-CHj-NHCS-NHPh 
(Johnson and Guest, J. Amer. Chem. Soc. 1910, 
32, 1279). Comp. also Kuntze (Arch. Pharm. 1908, 
246, 110). An interesting case of alcoholysis 
observed by Willstattei and Stoll (Annalen, 
1910, 378, 18) is the conversion of amorphous 
chlorophyll into crystalline chlorophyll by .ethyl 
alcohol in the presence of an enzyme ' chloro- 
phyUase,' which accompanies chlorophyll in 
plant tissues. The reaction consists in the 
replacement of the complex phytyl group by 
the simpler ethyl group 
COaH-CsiHjjNjMgCCOjMeXCOjCjoHssHEtOH 

siCjjHsjOH+COijH-OaiHajNiMgCCOaMeXCOjBt). 

J. J. S. 

HYDROMAGNESITE v. Magnesium. 

HYDROMETER v. Specific gsavity. 

HYDROPYRIN v. Synthetic dbuqs. 

ElYDROQUININE v. Veoeto-alealoids. 

HYDROQUINONE. HYDROTOLUQUINONE 
V. Phenol and its homoloques. 

HYDROQUINONE CARBOXYUC ACID v. 

PBOTOCATECHinO ACID. 

HYDROSOLS v. Colloids. 

HYDROSULPHITES v. Sulphub. 

HYDROXY ACIDS. Oxy acids. The organic 
hydroxy acids are derived from the oorrespon^ng 
non-hydroxylated acids by the replacement of 
one or more hydrogen atoms in the hydrocarbon 
radicle of the acid by the same number of 
hydroxyl groups. According as the hydroxyl 
group is introduced into a fatty radicle or into a 
benzenoid radicle, the resulting acid is an alcohol- 
acid or a phenol-acid. 

Hydeoxy Acids of the Aliphatic Series. 

There are several groups of hydroxy acids oi 
the aliphatic series and these will be discussed 
smaiim. 

I. Monohjdroxymonocarboxylie acids 

CnHan-^CTz-iQ g^ The most important members 

of this group are glycoUic, lactic, hydiacryUc, 
hydroxybutyric, and hydroxysteario acids ($.(>.)• 
They occur naturally, e.g. glycollio acid in un- 
ripe grapes and in the leaves of Ampelopsis 
{Vitis) kederacea (D. C), lactic acid in the 
juice of the muscles, in sour milk, in pickles 
and in the gastric juice. 

General methods of preparation. 

(i) By the careful oxidation of diprimary, 
primary secondary, and primary » tertiary 
glycols with dilute nitric acid or with platinum 
black and air, e.g. lactic acid from glycol. 

(ii) By the reduction of aldehyde a«ids, keto- 
acids, and dicarboxylio acids with sodium 
amalgam or with zinc and hydrochloric or 
sulphuric acids, e.g. lactic acid from pyroracemic 
acid and glycollio acid from oxalic acid. 

fiii) By boiling monohalogen fatty acid 



HYDROXY ACIDS. 



88 



with silver oxide, alkali, or with water or by 
distilling them, e.g. glycollic acid from mono- 
cUoroacetio acid ; hyiuacrylic acid from |3-chloro- 
propionic acid; 7-butyrolaotone from 7-ohloro- 
butyrio acid. 

(iv) By the action of nitrous acid on amino 
acids of the fatty series, e.g. glycollic acid from 
glycine. 

(v) By the action of hydrogen cyanide 
followed by hydrochloric acid on aldehydes, 
ketones, and glycolclUorhydrins, e.g. lactic acid 
from acetaldehyde ; hydracrylio acid from 
glyoolchlorhydrin. 

(vi) By treating unsaturated acids with 
hydxobromio acid, or with dilute sulphuric acid 
or by distilling them, e.g. 7-Yalerolactone from 
aUylacetic acid. 

Properties. — These acids may be sub-divided 
into three groups, primary, secondary, and 
tertiary acids, e.g. hydracrylic acid, 

^H ^H 

0H.(0H)-C-CO,H, lactic acid, CHj-C-COaH and 

^CH, 
a-hydroiyisobutyric acid, CHj-C-COOH. They 

also exhibit difierences in their properties de- 
pending on the position of the hydroxyl group 
in the molecule, i.e. whether they are o-, 3- or 
7-hydroxy-acids. They are more soluble in 
water, but less soluble in ether than the corre- 
spon^ng fatty acids. They are also leas vola- 
tile and, as a rule, cannot be distilled unchanged. 

General reactions. 

(i) Like the fatty acids they yield through 
change in the carboxyl group normal salts, 
esters, amides, and nitrUes. 

(ii) Like the alcohols, the hydrogen of the 
hydroxyl group may be replaced by alkali 
metala or by alkyl groups ; also by the 
action of acyl chlorides or of a mixture of con- 
centrated nitric and sulphuric acids, acid radicles 
or the nitro group may be substituted for it. 

(iii) Phosphorus pentachloride replaces the 
two hydroxyl groups by chlorine, e.g. glycollic 
acid yields chloracetylchloride^^ 

(iv) Hydriodic acid reduc^the hydroxy 
acids to the corresponding fatty acids, e.g. 
propionic acid from lactic acid. 

In the above reactions the hydroxy acids 
behave similarly, but on oxidation or by the 
application of heat, these acids show great 
differences. 

(v) On oxidation these acids yield different 
products, according as whethe^they are primary, 
secondary, or tertiary acids. 

(a) Primary acids yield aldehyde acids and 
dibasic acids, «.j. glycollic acid yields glyoxylio 
and oxalic acids. 

(5) Secondary acids yield ketonio acids ; the 
a-ketonic acids change to aldehyde and carbon 
dioxide, the S-ketonio acids to ketones and 
carbon dioxide, e.g. lactic acid yields pyruvic 
acid, which changes into acetaldehyde and 
carbon dioxide. 

(c) Tertiary o-hydroxy acids yield ketones, 
t.g. o-hydroxyisobutyric acid yields acetone. 

(vi) By the appUoation of heat, differences 
in deportment are shown by these acids, accord- 
ing as they are, o-, /3-, or 7-hydroxy acids. 

(o) a-Hydioxy acids lose water and become 
cyolio double esters — the lactides, e.g. lactic acid 



becomes laotide, two molecules of the acid 
condensing with the loss of two molecules of 
water. 

(6) iS-Hydroxy acids lose water and become 
unsaturated acids, e.g. hydracrylic acid becomes 
acrylic acid. 

(c) y and S-Hydroxy acids lose water at the 
ordinary temperature and change siore or less 
completely into simple cyclic esters — lactones. 

II. Aldehyde acids, Pormic acid is the 
simplest member of this group of sreids, and also 
of the fatty acid series. The next member is 
glyoxylic acid, OHO-COjH. Its claim to be 
considered here lies in the fact that all the salts 
are derived from the dihydroxy formula of 
glyoxyUo acid (OH)jOH-COjH, and thus it 
behaves both as an aldehyde acid and as a 
dihydroxy acid. For details as to this group of 
acids V. Glyoxylic acid. 

III. Monohydroxydicarboxylic acids 

C„H,„Li(OH)(CO,H),. 
Various groups of monohydroxydicarboxylic . 
acids are known, corresponding to the several 
groups of dibasic acids (q.v.). The most im- 
portant acids of this type are tartronic, 
malic, a-glutanic, and paraoonic acids. They 
occur in nature; thus malic acid in unripe 
gooseberries, and in rhubarb; a-hydroxy- 
glutaric acid in molasses. The acids in which 
the hydroxyl group occupy the 7 position with 
reference to the carboxyl group, when separated 
from their salts, readily part with water and 
become lactones, e.g. paraconic acid. The 
methods of preparation are very similar to those 
of the monobasic acids. 

IV. Dlhydroxydicarboxyllc acids. The most 
important acid of this group is tartaric acid 
{q.v.). Mesoxalic acid, which is ketomalouio 
acid, exhibits tautomerism and behaves both as 
a keto-acid and as a dihydroxy acid. 

V. Hydroxytricarboxylic acids. The most 
important acid of this group is citric acid (q.v.). 

Hydkoxy Acids of the Aromatic Series. 

If the hydroxyl group is attached to the 
benzene nucleus of a carboxy acid derived from 
benzene or its homologues, the acid thus formed 
is a phenol acid. Examples of tWs class are 
the three isomeric hydroxy benzoic acids, which 
have the formula C„Hj(OH)COOH. On the 
other hand, in the case of carboxy acids derived 
from homologues of benzene, a hydroxyl group, 
may be introduced into a fatty lateral chain, 
and in such a case the resulting acid is an alcohol 
acid ; such an acid is mandelic acid 
08H6-CH(OH)COOH. 

I. Monohydroxyaromatic acids. The most 
important members of this group of acids are 
salicylic, m- and p-hydroxybenzoic and anisic 
acids ii.v.). They occur in nature; thus sali- 
cylic acid is found in the buds of Spircsa 
Ulmaria {JAim.) and as the methyl ester in oil 
of winter-green. 

General methods of preparation. 

(i) By the action of nitrous acid on the 
amino-acids, e.g. salicylic acid from anthranilio 
acid. 

(ii) By fusing the sulphonic acids with alka- 
lis, e.g. salicylic acid from o-toluenesulphonio 
acid. 

(iii) By fusing the homologous phenols with 



80 



HYDROXY ACIDS. 



alkalis, when the methyl group attached to the 
benzene nucleus will be oxidised to the carboxyl 
group, e.g. saUcyllo acid from o-oresol. 

(iv) By fusing the phenol aldehydes with 
potash, e.g. salicylic acid from salicylaldehyde. 

(y) By the action of carbon dioxide on the 
dry s&dium salts of the phenols at high tempera- 
tures when the carbonic acid usually enters the 
ring in the position ortho to the hydroxy! group, 
e.g. salicylic acid from sodium phenate. 

(vi) By boiling the phenols with carbon tetra- 
chloride and caustic potash, the carboxyl group 
entering the ring generally in a position para to 
the hydroxyl groups : o-acids are formed in 
small' amounts, e.g. p-hydroxybenzoio acid from 
phenol, carbon tetrachloride and caustic potash. 

Properties. — ^When these acids react with 
carbonates only the hydrogen of the carboxyl 
group is replaced by metal ; but with alkaline 
hydroxides they behave like feeble dibasic 
acids, and the hydrogen of the phenoUo hydroxyl 
is also replaced : e.g. in disodium salicylate 
• C8Hi(0Na)C00Na. Carbon dioxide wiU convert 
the latter into the former. The o-aoids, unlike 
the m- and p-acids, volatilise in aqueous vapour, 
are coloured violet by ferric chloride and dis- 
solve in chloroform. The m-acids are coloured 
red brown when heated with concentrated 
sulphuric acid and are converted into hydroxy- 
anthraquinones : they are usually more stable 
than the o- and p-acids. Boiling hydrochloric 
acid decomposes the p-acids into carbon dioxide 
and phenols. AH the hydroxy acids decompose 
into phenol and carbon dioxide when distilled 
with Ume. 

II. Dihydroxyaromatic acids. The most im- 
portant member of this class is protocateohuic 
acid (q.v.). These acids may be prepared by 
the same methods as were used for the mono- 
hydroxy acids {v. supra). The carboxyl group 
is more readily introduced into the dihydroxy- 
benzenes than into the monohydroxybenzenes. 
This may be effected by heating the compounds 
with a solution of ammonium or sodium car- 
bonate at 100°-130°. The dihydroxybenzoic 
acids break down when heated, into carbon 
dioxide and dihydroxybenzenes. 

III. Tribydroxyaromatlo acids. The most 
important members of this group are gallic and 
tannic acids {q.v.). 

HYDROXYANTHBAQUINONE v. AiizAum 

AND ALLIED COLOTmorO MATTEES. 

HYDROXYBENZALDEHYDE v. Salicyl- 

ALDBHYDE. 

H^SROXYBENZENES v. Phenol and its 

HOMOLOGTJES. 

HYDROXYBUTYRIC ACIDS C^HjOj. 

o-Hydroxybutyric acid 

CHa-CHi,-CH(OH)COaH. 
Prepared by treating o-chloro- or a-bromo- butyric 
acid with baryta (Markownikow, Annalen, 163, 
242) or with moist sUrer oxide (Naumann, 
Annalen, 119, 115; Friedel and Machuca, ibid. 
120, 279) ; by treating- the oyanhydrin of 
propionaldehyde with hydrochloric acid and 
saponifying the nitrUe thus produced (Prbzibyek, 
J. Russ. Chem. Soo. 8, 335) ; by heating ethyl- 
tartronic acid at 180° (Guthzeit, Annalen, 209, 
234) ; by boiling 100 grams of o-bromobutyric 
acid, 600 c.c. of water and 1 molecular proportion 
of potassium carbonate for 6 to 6 hours (Bischofi 



and Walden, ibid. 279, 104). Forma white 
crystals, m.p. 43°-44°, sublimes at 60''-70° and 
boils at 225°. Chromic acid oxidises it to acetic 
and propionic acids, whilst electrolysis of a con- 
centrated solution of the sodium salt results in 
the production of propionaldehyde and formic 
acid (Miller and Hofer, Ber. 1894, 468). It has 
been resolved into its optically active components 
by fractional crystallisation of the brucine salts 
(Guye and Jordan, Compt. rend. 120, 662, 632, 
1274). 

/3-HydroxybntyTie acid 

CH,-CH(OH)CHaCOjH. 
Prepared by the reduction of aceto-acetio ester 
with sodium amalgam (Wislicenus, Annalen, 
149, 205) ; by the action of potassium cyanide 
on a-propylenechlorhydrin and saponification of 
the nitrUe thus formed (Markownikow, ibid. 153, 
237). It forms a thick syrup, which is volatile 
in steam and on heating decomposes into water 
and crotonic acid. It has been resolved into 
its optically active components by fractional 
crystallisation of the quinine salts (McKenzie, 
Chem. Soc. Trans. 1902, 1402). Z-^B-Hydroxy- 
butyric acid occurs in the urine in considerable 
quantities in cases of diabetes mellitus (Laud, 
Chem. Zentr. 1899, ii. 63; Bergell, Zeitsch. 
physiol. Chem. 1901, 33, 310; Minkowski, 
Chem. Soc. Abstr. 1885,413; KuIz, Zeitsch. Biol. 
20, 165). (For estimation in mine v. Schaffer, 
J. Biol. Chem. 1908, 6, 211 ; Black, ibid. 207.) 
The liver cells contain an enzyme, $-hydr<xcy- 
biUyrase, which converts ;8-hydroxybutyric acid 
into aceto-acetic acid (Wakeman and Dakin, 
ibid. 1909, 6, 373). 
- 7-Hydroxybutyrlc acid 

CHj(OH)CHa-CHj-COsiH 
readily loses water even at the ordinary tem- 
perature passing into the cyclic ester, butyro- 

lactone CHj-CHa-CHj-CO-O. Butyrolactone was 
discovered by Saytzeff in 1873, but he regarded 
it as the dialdehyde of succinic acid. He pre- 
pared it by the reduction of sucoinyl chloride in 
acetic acid withjiodium amalgam (Annalen, 171, 
261). It maySso be prepared by the distilla- 
tion of 7-chlorobutyric acid at 180°-200° (Henry, 
Bull. Soc. chim. [ii.]46, 341); by the interaction 
of ethylene ohlorhydrin and acetoacetic ester and 
decomposing the resulting product with baryta 
(Chanlaroff, Annalen, 226, 325) ; by treating a 
solution of succinic anhydride in ether with 
sodium amalgam and gradually adding hydro- 
chloric acid to tke product (Kohter and Her- 
brand, Ber. 1896, 1192) ; by heating 7-phenoxy- 
butyric acid with fuming hydrobromio acid 
(Bentley, Haworth and Perkin, Chem. Soc. Trans. 
1896, 168) ; by the reduction of aldehydopro- 
pipnic acid with sodium amalgam (Perkin and 
Spraukling, ibid. 1899, 17). It is a colourless oil, 
b.p. 206° (Fittig and Boeder, Annalen, 227,22); 
sp.gr.l-128615°/0°; itisvolatileinsteam. Chromic 
acid Oxidises it to suooinio acid ; heating with 
hydriodio acid converts it into iodobutyno acid 
(Saytzeff, J. pr. Chem. 25, [ii.] 70). It reacts 
with magnesium methyl iodide, forming 
S-methylpentane-oS-diol (Henry, Comnt. rend. 
1906, 143, 1221). " 

o-Hydroxyisobutyrie acid (Butyl-lactinic acid, 
Acetonic acid, Dimethyl oxalic acid) 
(CH,),C(OH)-rO,H. 



HYDROXYLAMINE. 



8^ 



Prepared by treating aoetone with prussio and 
hydroohlorio aeida (Staedder, Annalen, 111, 
320; Markownikow, ibid. 146, 339); by 
treating dimethyloxalic ester with . zinc and 
methyl iodide (I^ankland and Duppa, ibid. 135, 
25) ; by heating aoetoneohloroform to 180* with 
water or by boiEng with caustic soda (Willgerodt 
and SchifE, J. pr. Chem. 41, [ii.] 519 ; Ber. 1882, 
2307) ; by heating a-bromo- or o-oliloroisbbutyrio 
acid with water to. 180°, with baryta, or with 
caustic soda (Markownikow, Annalen, 153, 228 ; 
Fittig, ibid. 200, 70; Ostropjatow, J. Euss. 
Phys. Chem. Soo. 28, 61) ; by treating o-amino- 
t'sobutyi^o acid with soium nitrite (Tiemann 
and Friedlander, Ber. 1881, 1973) ; by treating 
isobutyric acid with potassium permanganate 
(Meyer, Annalen, 219, 240). It forms hygro- 
scopic prisms which sublime at about 60°, and 
when freshly sublimed melt at 79° ; -b.p. 212° ; 
volatile in steam. Oxidation with chromic Acid 
converts it into acetic acid, acetone, and carbon 
dioxide ; fusion with caustic soda yields acetone ; 
heating with phosphorus pentozide yields 
acetaldehyde, acetone, acetic acid, and other 
products (BischoS and Walden, Annalen, 279, 
111). Acetone chloroform {q.v.) 

(CH,),C(0H)CC1, 
is an interesting derivative of this acid. 

HYDROXYLAMINE NHaOH. Discovered 
by Lessen (Annalen, Suppl. 1868, 6, 220) in 1866, 
but until 1891 only known in the form of 
salts or in aqueous solution. Obtained by the 
reduction of nitrio acid with metals under 
suitable conditions (Divers, Chem. Soo. Trans. 
1883, 443 et seg. ; 1885, 697 et aeq.); by the 
reduction of nitrates, nitro bodies, &c., with 
finely divided metals (Wohl, Eng. Pat. 11216 ; 
J. Soc. Chem. Ind. 1895, 595) ; by the electrolytic 
reduction of nitric acid, nitrous acid, or their 
salts or other derivatives in the presence of a 
second acid electrolyte at a low temperature 
(BoehringerandSohne, D. R. PP. 133457, 137697; 
Er. Pat. 319187 ; J. Soo. Chem. Ind. 1902, 1458 ; 
Compagnie Parisienne de Couleurs d'Aniline, 
Fr. Pat. 322943 ; J. Soc. Chem. Ind. 1903, 425 ; 
Tafel, Zeitsch. anorg. Chem. 1902, 31, 289) ; by 
the reduction of nitrites with sodium amalgam 
(Divers, Chem. Soc. Trans. 1899, 89) or with 
sulphites (Baschig, Eng. Pat. 3028; J. Soc. 
Chem. Ind. 1888, 210 ; EiohkofE, Arch. Pharm. 
27, [iii.l 713 ; LidofE, J. Russ. Chem. Soc. 1884, 
751 ; Divers and Haga, Chem. Soo. Trans. 1887, 
661; 1896, 1666). It is best prepared by 
taking a concentrated aqueous solution of com- 
mercial sodium nitrite (2 mols.) and sodium 
carbonate (1 mol.) and passing in sulphur 
dioxide at —2° to —3° with constant stirring 
until it is just acid. The solution is warmed 
gently with a few drops of sulphuric acid and 
then kept at 90°-96° for two days. - It is then 
neutralised with sodium carbonate, evaporated 
until the solution weighs about 10|--11 times^s 
much as the sodium nitrite originally taken, 
when on cooling nearly all the sodium sulphate 
crystallises out. The hydroxylamine sulphate 
is obtained from the mother liquors and purified 
by recrystallisation (Divers and Haga, I.e.). 
Jouve (Compt. rend. 128, 434) -has prepared 
hydroxylamjne synthetically by the direct 
union of hydrogen and nitric acid in the presence 
of spongy platinum at 115°-120°. The anhy- 
drbus compound may be obtained by dissolving 



hydroxylamine hydrochloride in absolute methyl 
alcohol, adding a solution of sodium methoxide 
in the same solvent, separating the sodium 
chloride so formed and distilling oS the greater 
part of the methyl alcohol under 100 mm. 
pressure. The- residue is distilled in small 
portions under 20 mm. pressure with' the 
addition of a little vaseUne to prevent frotliing. 
When the solid hydroxylamine begins to come 
over, the receiver is changed and cooled to 0°, 
care being taken that the hydroxylamine vapour 
does not come in contact with air at 60°-70°, 
as then explosions occur (Lobry de Bruyn, Eeo. 
trav. chim. 10, 100 ; 11, 18 ; v. also Brtihl, Ber. 
1894, 1347). Crismer (Bull. Soc. chim. 6, [iii.] 
793) obtains it by heating zinc dihydroxylamine 
chloride, and Dhlenhuth (Annalen, 311, 117) by 
the distillation of the phosphate under reduced 
pressure; the solid thus obtained may be 
purified by crystallisation from absolute alcohol 
at —18° (Ebler and Schott, J. pr. Chem. 1908, 
78, [ii.l 289). 

Hydroxylamine forms white inodorous scales 
or hard needles, sp.gr. 1-3 (circa), m.p.- 33-05°, 
b.p. 68° under 22 mm. Heated to 100° it 
decomposes, ammonia, nitrous and hjrpouitrous 
acids being the first products of decomposition 
and these then interact with the formation of 
nitrogen and nitrous oxide. Readily soluble in 
water; and to a less extent in ethyl and methyl 
alcohols, and in boUiug ether (De Bruyn, Ber. 
1894, 967). When pure it is stable below 15°, 
but alkali decomposes it. The aqueous solution 
is colourless and odourless, has a strong alkaline 
reaction, and gives precipitates, insoluble in 
excess, with salts of Zn, Ni, Fe, Al, Cr, but not 
with those of the alkaline earths. In its general 
reactions resembles a solution of ammonia, 
although it is less basic than that substance. 
It acts as a strong reducing agent, e.g. with 
CuSOj solution it gives a red precipitate of 
CugO ; it reduces Hgd, to HgQ, and precipi- 
tates the metals from solutions of AgNO,, AuCl,, 
and PtCl4. It can also act as an oxidising agent 
being itself reduced to ammonia (Haber, Ber. 
1896,2444; Biltz, t7ii<2. 1896, 2080 ; Dunstanand 
Dymond, Chem. Soo. Trans. 1887, 646). Thus 
in alkaline solution it converts ferrous hydrox- 
ide into ferric hydroxide, whilst in acid solu- 
tion it reduces ferric chloride to ferrous chloride. 
Oxidation converts hydroxylamine into nitrous 
oxide and nitrio oxide (Arudt, Ber. 1900, 33) and 
caustic soda decomposes it into nitrogen, nitrous 
oxide, nitrous acid and water (Kolotofi, J. Russ, 
Phys. Chem. Soc. 26, 295). 

The salts of hydroxylamine are readily 
soluble in water and alcohol; they crystallise 
well and are anhydrous. 

By treating hydroxylamine sulphate-in the 
cold with sodium nitrite and then adding sUver 
nitrate, a yellow precipitate of silver hypo- 
nitrite is obtained (Wislicenus, Ber. 1893, 771 ; 
Tanatar, J. Russ. Phys. Chem. Soo. 26, 342 ; Ber. 
1894, 187). By passing sulphur dioxide through 
a solution of the hydrochloride or sulphate, 
ammonium sulphate is produced (Tanatar, Ber. 
1899, 241, 1016). Elber and Schott (J. pr. Chem. 
1908, ii. 78, 289) have prepared metaUio salts of 
the type R(ONH2)2, where R is any divalent 
metal : alkyl hydroxylamines have been pre- 
pared by the action of alky] halides on hydroxyl- 
amine (Dunstan and Goulding, Chem. Soc. Trans. 



HYDBOXYLAMINE. 



1899, 792 ; V. also ibid. 1896, 839 ; De Bruyn, 
Reo. trav. ohim. 16, 185). 

Detection ahd estimation. — Hydroxylamine 
may be detected by its action in reducing 
Fehling's solution with the formation of cuprous 
oxide (Adams and Overi^an, J. Amer. Chem. Soo. 
3J, 637); by adding sodium nitroprusside to a 
neutiai solution and then a, little caustic soda, 
when a magenta red colouration is produced 
(Angeli, Gazz. chim. ital. 23, ii. 102) ; 'or by 
treating it with sodium acetate and benzoyl 
chloride with the formation of benzhydroxamio 
acid which gives a violet red colouration with 
ferric chloride (Bamberger, Ber. 1899, 1805). 
It may be estimated by titration in alkaline 
solution with mercury acetamide, which is re- 
duced to metallic mercury (Forster, Chem.Soc. 
Trans. 1898, 786) ; by oxidation with vanadio 
sulphate, measuring the nitrogen evolved and 
titrating the vanadous sulphate with potassium 
permanganate (Hofmann and Kiispert, Ber. 
1896, 64) ; by adding excess of standard 
titanium trichloride and titrating back the 
excess with potassium permanganate (Stahler, 
ibid. 1904, 4732 ; v. also ibid. 1909, 2695) ; by 
titrating the solution with potassium per- 
manganate after the addition of sodium oxalate 
(Simon, Compt. rend. 135, 1339); by boiling 
, with excess of N/10 silver nitrate solution, am- 
monia, and caustic soda and estimating the 
silver nitrate unacted upon (Denigfe, Ann. Chim. 
Phys. 7, [vi.] 427). Jones and Carpenter (Chem. 
Soc. Trans. 1903, 1394) add the solution con- 
taining the hydroxylamine to a hot solution of 
potassium copper carbonate or tartrate with 
stirring. The solution is boiled, filtered, the 
precipitate washed with hot water and dissolved 
in ferrous sulphate in an atjnosphere of carbon 
dioxide. The ferrous salt is titrated back with 
potassium permanganate. 

4 mols. K2Mn2Og=10 mols. NHjOH. 
gchaefier (Bull. Mulhouse, 1883) has ap- 
plied the reducing properties of hydroxyl- 
amine in order to discharge manganese brown. 
The hydrochloride NH20H,H;a must be used. 
On printing this upon a manganese ground the 
latter is instantly reduced to manganese chlor- 
ide. A very dark indigo, blue-dyed on man- 
ganese, is lowered to a lighter and brighter blue 
by the elimination of the MnOj;. , In like manner 
nankin, chamois, and similar colours can be 
discharged white (J. Soc. Chem. Ind. 3, 166). 

Hydroxylamine and its salts have been used 
as developers in photography, and for recovering 
silver from fixing bath solutions and waste 
liquor^ (Lainer, J. Soc. Chem. Ind. 1890, 890). 
It is a powerful antiseptic (Marpmann, Pharm. 
Centr. N.F. 10, 245) and has been used as a 
substitute for chrysarobin and pyrogallio acid, 
as it does not discolour the skin or bandages 
and has a strong reducing action (Sohwarz, 
Pharm. Zeit. 33, 659). 

Etbylhydroxylamlnes v. Ethvl. 
^-Phenylhydroxylamine CeH^NHOH. Pre- 
pared by the reduction of nitrobenzene (1) in 
water with zinc (Bamberger, Ber. 1894, 27, 
1348, 1548 ; Wohl, ibid. 1432) ; (2) in alcohol 
with zinc (Wohl, ibid. 1434 ; D. E. P.' 84138 ; 
Frdl. iv. 44), or the zinc-copper couple (Wohl, 
D. R. P. 84891 ; Md. 46) in the presence of 
anhydrous calcium chloride ; (3) in aqueous 



alcohol with zinc amalgam in the presence of 
aluminium sulphate (Bamberger and Knecht, 
Ber. 1896, 29, 864) ; (4) in ether with zinc in the 
presence of anhydrous calcium chloride (Gold- 
Echmidt, ibid. 2307) ; (5) in aqueous ether with 
alumiftium amalgam (Wislioenus, ihid. 494; 
J. pr. Chem. [ii.] 64, 67) ; (6) in ammonium 
chloride mth zinc (Kalle & Co. D. R. P. 89978 ; 
Frdl. iv.' 47)-; (7) electrolytibaUy in acetic acid 
(Haber, Zeitsoh. Elektrochem. 1898, 6, 77) or 
in alcoholic ammonia (Schmidt, Zeitsch. physikaL 
Chem. 32, 272) ; by the oxidation of aniline in 
ethereal solution with Caro's acid (Bamberger 
and Tschimer, Ber. 1899, 32, 343). , 

;8-Phenylhydroxylamine forms colourless 
needles, m.p. 81°-82''; soluble in 10 parts of 
hot and 60 of cold water, readily soluble in 
alcohol, ether, carbon disulphide, and chloro- 
form, sparingly so in petroleum. It dissolves 
in sulphuric acid with a deep blue colour. By 
heating at 100° azobenzene together with 
aniline, azoxybenzene, and other products are 
formed. Oxidation with potassium permanga- 
nate gives first nitrosobenzene, then nitrogen 
and azoxybenzene (Bamberger and Tschimer, 
Ber. 1899, 32, 342) ; in dilute neutral solution 
hydrogen peroxide yields azoxybenzene, in 
alkaline solution azoxybenzene and nitrobenzene 
(Bamberger, ibid. 1900, 33, 119). In the 
presence of .hydroxylamine and air it is "partly 
oxidised to azo^benzene and partly reduced 
to aniline, phenylazoimide, and benzeneazo- 
hydroxyaailide ako being formed (Bamberger, 
ibid. 1902, 35, 3893). It dissolves in sodium 
hydroxide forming a sodium salt which in the 
absence of air jrields azoxybenzene, and in the 
presence of air azoxybenzene and nitrobenzene ; 
alcoholic potash yields azobenzene (Bamberger 
and Brady, ibid. 1900, 33, 271). Mineral acids 
yield j)-amihophenol and azoxybenzene ; alco- 
holic sulphuric acid gives azoxybenzene, o- and 
j>-phenetidine, o- and })-aminophenol3, aniline 
and other compounds (Bamberger and Lagutt, 
ibid. 1898, 31, 1501). With aromatic aldehydes 

CHR\ 
it yields phenylaldoximes of the type I >0 

NPh^ 
(Plancher and Piccinini, Atti. R. Acad, Ijncei. 
1905, [v.] 14, ii. 36). (For constitution, v. Bruhl, 
Zeitsch. physikal. Chem. 1898, 26, 47.) 

Nitrosophenylhydioxylamine C,HeN(NO)OH. 
Prepared by the action of sodium nitrite and 
dilute sulphuric acid on /3-phenylhydrpxylamine 
(Wohl, Ber. 1894, 27, 1435; Bamberger, ibid. 
1563) ; or by the interaction of hydroxylamine 
and nitrobenzene in alcoholic solution in the 
presence of sodium ethoxide (Angeli, ibid. 1896, 
29, 1885 ; Angelico, Atti. R. Aocad, Lincei, [v.] 
8, u. 28). 

It crystallises from petroleum in colourless 
needles, melting at 68°-59° and decomposing 
at* 75°; sparingly soluble in water, readily so 
in most organic solvents. On heating it decojn- 
poses into nitrosobenzene and other substances 
(Bamberger, Ber. 1898, 31, 574, 1607). Alcoholic 
or ethereal solutions give a brownish-red coloura- 
tion with a few drops of dilute ferric chloride 
(Bamberger and Ekeorantz, ibid. 1896, 29, 
2412). Reduction with sodium amalgam yields 
phenylhydrazine ; oxidation with potassium 
permanganate or sodium hypochlorite, nitroso- 
benzene. By heating with dilute mineral acids 



HYDROXYSTEABIC ACIDS. 



89 



niti'oso benzene is formed, whilst nitrous aoid 
yields benzenediazonium nitrite. 

CapIeTTOn, Ammonium nitrosophenylhydroxyl- 
amine, is prepared by dissolving ;8-phenylhy- 
droxylamine in ether at 0°, passing in dry 
ammonia and adding excess of amyl nitrite, 
when a snow-white crystalline mass of ammonium 
nitrosophenylhydroxylamine is formed (Baudisoh 
and King, J. Ind. Eng. Chem. 1911, 3, 629). 

Cupferron is used in quantitative analysis for 
separating copper and iron from most of the 
metals. The iron and copper are precipitated 
in strongly acid solution with cupferron, the 
precipitate filtered, washed with water, and 
finally with ammonium hydroxide. The latter 
dissolves the copper, but not the ferric salt. 
The ferric salt is soluble in chloroform, ether, 
acetone, &c., and may be dissolved and separated 
from other salts, such as those of lead, silver, or 
tin, which may have been precipitated vrith it 
(Baudiach, Chem. Zeit. 1909, 33, 129S ; Biltz 
and Hodtke, Zeitsch. anorg. Chem. 1910, 66, 
426 ; HanuB and Soukup, ibid. 68, S2 ; Eresenius, 
Zeitsch. anal. Chem. 1911, 50, 35). The use of 
cupferron as an analytical reagent is limited by 
virtue of its explosive properties. 

HYDROXYQUINOL v. Phenol and its 

HOMOLOOtrBS. 

HYDROXYQUINOLINE v. QunroLraB. 

HYDROXYQUINONE COLOURING MAT- 
TERS. The hydroxyquinones form an im- 
portant group of mordant colouring matters 
which are characterised by containing at least 
one hydroxyl group adjacent (ortho- or peri-) 
to an oxygen atom of a quinone, but usually 
two hydroxyl groups in the ortho- position 
with respect to one another. They possess the 
property of forming insoluble, coloured salts 
with certain metallic oxides, and therefore, when 
dyed on a fabric impregnated (mordanted) with 
such oxides, for example, the oxides of alu- 
minium, chromium, and iron, lakes are formed 
which are extremely fast. The simplest com- 
pound possessing the above requirements is 
tetrahydroxy-p-benzoquiuone 
OH OH 



0: 



<;>» 



OH OH 

but its dyeing properties are not sufficiently 
intense for it to be of practical value. This 
desideratum is first reached in the naphthalene 
series in the case of dihydroxynaphthaquinone 
O 



OH 




lOH 







which comes on the market under the name of 
Naphthazarin (see under Naphthaibne). 

By far the most valuable and important 
hydroxyquinones are those belonging to the 
anthracene series, of which a large number are 
manufactured. The simplest and best known 
of these is dihydroxyanthraquinone or alizarin 
OH 

/y-co^YXoH 

V/\C0/-X/ 
(See Alizakin colouring mattebs.) J. 0. C. 



HYDROXYSTEARIC ACIDS CisHjeOj. 

a-Hydroxystearie acid 

CH3[CHjl,5CH(OH)COaH. 
Prepared by treating o-bromostearic aoid with 
aqueous potash. Separates from a mixture of 
benzene and petroleum as a crystalline powder, 
m.p. 91°-92° (Hell and Sadomsky, Ber. 1891, 
2391 ; Le Sueur, Chem. Soo. Trans. 1904, 827). 
By heating it to 270°, it yields margaric aldehyde 
CieHjj-CHO, a lactide CsjHejO,, formic aoid, 
water andtarbou dioxide. 

iS-Hydroxystearic acid 

CH,[CHJ„CH(0H)CH2-C0i,H. 
Prepared by treating iS-bromstearic acid with 
aqueous potash. Crystallises from chloroform 
in white plates, m.p. 89° (Ponzio, Atti. E. Aooad. 
Sci. Torino, 1905, 40, 970). 

7-Hydioxystearic acid exists only in the form 
/^CH2'CH3. 
o£ a lactone CH,[CHj], ,CH ^^ | Ob- 

^-OCO 
tained by treating the anhydride of 7-hydroxy- 
oleic acid with potash (Geitel, J. pr. Chem. 37 
[ii.] 85). Prepared by heating oleic aoid with 
anhydrous zinc chloride. Oxidation with 
chromic acid in glacial acetic aoid converts it 
into liquid monobasic and small quantities of di- 
basic acids, including succinic acid and 7-keto- 
stearic aoid CH8[CH2], aCOrCHal jCOaH, m.p. 
97° (Shukofi and Sohestakoff, J. Buss. Phys. 
Chem. Soo. 1903, 35, 1). 

i-Hydroxystearie acid 

CH3[CH2],-CH(OH)[CHj],CO,H. 
This" acid was formerly described as p-hydrox- 
stearic acid (A C. nd M. Saytzew, J. Buss. Phys, 
Chem. Soc. 1886, 328 ; 17, 426 ; J. pr. Chem, 
35, [ii.] 369, 384 ; Tremy, Annalen, 19, 296 ; 20, 
50; 33, 10; Ann. Chim. Phys. 65, [ii.] 113 
Sabanejew, J. Buss. Phys. Chem. Soo. 18, 41 
Geitel, J. pr. Chem. 37 [ii.] 81 ; Leiohti and 
Suida, Ber. 1883, 2458). Shukoff and Schesta- 
ko£E (J. Buss. Phys. Chem. Soc. 1903, 35, 1) 
have shown that its constitution is that of 
i-hydroxystearic acid. It is prepared from the 
aulpho or iodo derivative of oleic acid, or best 
by the action of sulphuric acid on oleic acid ; 
m.p. 83°-85°. It may also be obtained from 
elaidic acid by the action of sulphuric acid and 
subsequent treatment with alcoholic potash 
(Tscherbakow and Saytzew, J. pr. Chem. 57, [ii.] 
27). By heating to 100° it yields an anhydride ; 
oxidation with chromic acid iij glacial acetic aoid 
converts it into sebaoic, azelaic, and traces of 
suberic and liquid monobasic acids and i-keto- 
stearic acid CH3[CHj],CO[CH2],COjH, m.p. 
76°. Molinari and Barosi (Ber. 1908, 2794) 
have obtained an acid by the decomposition of 
the ozonide of oleic acid and consider it to be 
formed by the aldol condensation of monalde- 
hyde with nonoic acid, and hence they consider 
it to i-hydroxystearic acid ; it melts at 41°, and 
bence is either impure or a hydroxystearic acid 
containiug the hydroxyl group in some other 
position. 

K-Hydroxystearic acid 

GH3[CHj]eCH(OH)[CHii]9COaH. 
This acid was formerly described as a-hydroxy- 
stearic acid (Saytzew, J. pr. Chem. 37, [ii.] 277, 
284). Shukoff and Schestakoff (J. Buss. Phys. 
Chem. Soo. 1903, 35, 1) have shown that its 



90 



HYDROXYSTBAEIC ACIDS. 



constitution is that of K-hydrozysteario acid ; 
m.p. 84°-85°. Prepared by the action of sul- 
phuric acid on isooleic acid. Oxidation with 
chromic acid in glacial acetic acid yields sebacic 
acid, nonylene-ai-dicarbozylio acid (m.p. 124°) 
and K-ketostearic acid, 

CH,[CHJ,CO[CHj],COjH, 
m.p. 65°. 

A-Hydroxysteade acid (12-Bydroxystearic 
acid) 

CH,[CH,]5CH(0H)[CH,],„C0^. 
Prepared from the methyl ester which is obtained 
by the reduction of the methyl ester of ricinoleio 
acid ; m.p. 78° (Griin and Woldenberg, J. Amer. 
Chem. Soc. 1909, 31, 490). Kasansky (J. Kusa. 
Phys. Chem. Soc. 1900, 32, 149) by acety- 
lating ricindleic acid, followed by bromlnation 
and reduction^ obtained a hydrozystearic acid 
(m.p. 81°-82°) which is possibly identical with 
the aboye. 

HYDURaiC ACID C8H,08N4,H,0 or 2HjO ; 

CO<Ji:g8>CH.CH<gO:N^CO. was 

first prepared by Sohlieper (Annalen, 1845, 
56, 11), who obtained the acid ammonium salt 
together with alloxan by the action of nitric 
acid (sp.gr. 1-25) on uric acid. It is also pre- 
pared (2) in the form of its ammonium salt by 
prolonged boiling of alloxan or alloxantin with 
very dilute sulphuric acid (Finch, Annalen, 
1864, 132, 303); (3) by heating crystallised 
aUoxantin in a tube at 170° when it is converted 
quantitatively into hydurilic acid, according to 
the equation 
2C3H40,N,+3HjO 

=C8H,0,N.+4NH,+(COOH),-|-2eO-l-4COs 
or alloxan is similarly decomposed (Murdoch and 
Doebner, Ber. 1876, 9, 1102) ; (4) in the form of 
its acid ammonium salt by heating dialuric acid 
with glycerol at 150°, formic acid and carbon 
dioxide being formed at the same time (Baeyer, 
Annalen, 1863, 127, 14); (6) together with 
glycine and carbon dioxide by heating uric acid 
with twice its weight of concentrated sulphuric 
acid (Schultzen and Filehne, Ber. 1868, 1, 150) ; 
(6) by reducing dibromobarbituric acid with 
hydrogen iodide (Baeyer, Annalen, 1864, 130, 
133) ; . and it is also formed to a small extent by 
reducing alloxantin with sulphuretted hydrogen 
(Murdoch and Doebner, I.e.) ; (7) by the con- 
densation of ethyl ethanetetraoarboxylate with 
carbamide in the presence of sodium ethoxide at 
60°-70° ; or by tke hydrolysis of ethanetetra- 
carbonylguanide 

^-=<S:cS>KS:S>«=^.-»o 

by means of dilute hydrochloric acid at 150° 
(Conrad, Annalen, 1907, 365, 24). Hydurilic 
acid is most conveniently purified by precipitat- 
ing the sparingly soluble copper salt from a 
solution of the neutral ammonium salt, and 
decomposing this with hot hydrochloric acid, in 
which the hydurilio acid is only slightly soluble 
(Baeyer, Annalen, 1863, 127, 16). 

Hydurilic acid crystallises from hot water in 
small four-sided prisms containing 2HgO, or is 
precipitated as a fine crystalline powder con- 
taining 1H,0 by the addition of hydrochloric 
acid to a hot aqueous solution. It is sparingly 
soluble in alcohol or cold water, more readily 
so in hot water ; its heat of combustion is 



658-5Cal. (Matignon, Ann. Chim. Phys. 1893, [vi.] 
28, 328). 

Hydurilio acid bears the same relation to 
dialuric and barbituric acids that alloxantin 
bears to alloxan and barbituric acid. Conrad 
(Aimalen, 1907, 365, 24) has shown that its con- 
stitution is correctly represented by the formula 

C<^i88>CH-^<88:^^CObyita 

synthesis from ethyl ethanetetraoarboxylate 
and carbamide {v. supra), and also by the 
fact that on hydrolysis with concentrated 
hydrochloric acid at 200°-230° it is converted 
ajinost quantitatively into carbon dioxide, 
ammonia, and succinic acid; barbituric acid 
when similarly treated yields carbon dioxide, 
ammonia, and acetic acid. 

Hydurilio acid is not attacked by reducing 
agents ; it yields alloxan and dibromobarbituric 
acid when treated with bromine. 

Fuming nitric acid oxidises it into alloxan, 
whilst weaker acid converts it into nitrobarbiturio 
acid (diliturio acid), tsonitrosobarbituric acid 
(violuric acid) and violantin. Ferric chloride or 
silver oxide oxidises it to oxyhydurilic acid, 
which gives a blood-red colouration with ferric 
chloride. Hydurilio acid has marked acidic 
properties, and decomposes most metallic 
chlorides and acetates, yielding the corresponding 
hydrogen hydurilate. The heat of neutralisa- 
tion of hydurilic acid with 2 mols. potassium 
hydroxide is 21-8CaI. ; but on adding a further 
quantity of alkali (up to 16 mols.) there is a 
further evolution of 4-2Cal. of heat, thus pointing 
to the existence of a third very feeble acid 
function. The following salts have . been 
described : the ammonium hydrogen salt 

NH.-CaH.OeN., 
small octahedral sparingly soluble crystals 
precipitated by acetic acid from solutions of the 
normal ammonium salt (NH,)2CsH40,N( which 
crystallises in needles with IHgO oi in large 
monoolinio crystals with 4H2O, a:b:c= 
1-0821 : 1 : 0-7003. Sodium salt 

crystallises in prisms; potassium hydrogen salt 
KCgHjOjNj forms sparingly soluble microscopic 
needles ; the nortnal salt E2C8H40,N(,3H30 is 
soluble and crystallises in prisms (Matignon). 
The. calcium salts Ca(CsH,0,N«)j,8H20 and 
CaC,H40gN4,3H20 are crystaUine and almost 
insoluble ; the barium salt BaCgHfO^NtiHgO ; 
the zinc salts Zn(CgHeO,N4)2 anid 
ZnC8H40,N4,2H,0 
are crystalline ; the copper salt 

Cu(C,H50eN4)2,8H30 
forms fine yellow needles or piisms, which 
become reel on heating with loss of water. The 
silver salt is unstable ; the ferric salt is a dark 
green precipitate, and the formation of a dark 
green colour with ferric chloride is a characteristic 
reaction of the salts of hydurilic acid ; ^he/errous 
salt is white becoming green ; the lead salt is 
insoluble in acetic acid. 

Dichlorohydurilic acid CgH4Clj04N4,2HjO is 
obtained by the action of potassium chlorate 
on an intimate mixture of hydurilic and con- 
centrated hydrochloric acids (Baeyer, Annalen, 
1863, 127, 26). It is a sparingly soluble powder, 
soluble in concentrated smphurio acid and 



HYPOXANTHINE OR SARCINE. 



91 



precipitated therefrom by the addition of water, 
in small rhombic crystals containing 2HjO ; it 
is readily decomposed by alkalis yielding the 
metallic chloride. The potassimn salt 

■ KjC8H8Cls,0„N4,2H,0 
is a sparingly crystalline soluble powder. 

TetramethylhydurUic acid (deoxyamalic acid) 
CjHi.O.N.; 

c<i^::88>H.cH<oo:NMc^co 

is obtained by the dry distillation of amalio 
acid (Fischer and Beese, Annalen, 1883, 221, 
339), or more conveniently by heating it in a 
sealed tube for 3 hours at 180°-185° (Matignon, 
Compt. rend. 1893, 116, 642) ; has also been 
obtained by heating dimethylpseadouric acid 
with fused oxalic acid at 170° (Fischer and 
Ach, Ber. 1895, 28, 2473). Deoxyamalic acid 
is crystalline, has m.p. 260°, with decomposition 
and can be distilled, although with partial 
decomposition. It is almost insoluble in not or 
cold walfer; readily soluble in chloroform or 
acetic acid ; its heat of combustion is 1321-8 Cal. 
(Matignon, Ann. Chim. Phys. 1893, [vi.] 28, 327). 
Its chemical properties are similar to those of 
hydnrilic acid, it reduces ammoniacal silver 
nitrate solution on warming, and gives a beauti- 
ful green colouration with ferric chloride; on 
gentle oxidation it yields a product that gives a 
blood-red colouration with ferric chloride ; but 
when oxidised by nitric acid it forms dimethyl- 
alloxan. 

Deoxyamalic acid has only two acidic func- 
tions; the 'potassium KjCigHj^OgNi and the 
sodium salt NajCijHuOjNj are sparingly 
soluble (Matignon, I.e. ; Fischer and Ach, 2.c.). 

M. A. W. 

HT6RINE V. VBQETO-ALKALOrDS. 

HYOSCYAMINE and HYOSCYAMUS v. 
Datuea ; Henbane ; and Vegbto-alkaloids. 

HYOSEINE V. Vegeto-alkaloids. 

HYPNAIi V. Stnihbtic drugs. 

HYPNONE V. Ketones ; Synthetic deuos. 

HYPONITRITES v. Nitrogen. 

HYPOPHOSPHITES v. Psosphoeus. 

HYPOSULPHITES v. Sulphue. 

HYFOXANTHINE oi SARGINE, G-oxypurine 
N:C(OH)-C-NHv NHCOC-NH\ 

1 • 11 >CH or 1 II >CH, 

CH : N G—W CH:N— O— N^ 

discovered by Scherer (Annalen, 1850, 73, 328) 
in milk, spleen, and blood, is widely distributed 
both in the animal and vegetable kingdoms. 
Strecker (Phil. Trans. 1858, 10, 121) isolated it 
from meat juice, and hence called it earcine; it 
was afterwards found to be identical with 
Scherer's hypoxanthine. It is a normal con- 
stituent of bone marrow (Heymann, Pfliiger's 
Archiv. 6, 184), glands, muscles, liver, brain 
(Salomon, Ber. 1878, 11, 674; Kossel, Chem. 
Zentr. 1881, 486), blood (Soberer, I.e. ; Salomon, 
Chem. Zentr. 1878, 681) and urine (Strecker, 
I.e. ; Salomon, Zeitsch. physiol. Chem. 1887, 11, 
410), the amount varying from 0-024 p.o. in the 
grey matter of the brain (Kossel, I.e. ) to 0-218 p.c. 
in the calf's thymus (Schindler, Zeitsch. physiol. 
Chem. 1889, 13, 432). Piccard found 6-8 p.c. 
of hypoxanthine and guanine in salmon roe 
(Ber. 1874, 7, 1714)i whilst ox testis and the 
spermatozoa of carp contain 0-281- and 0-309 p.c. 
respectively of the former base (Schindler, I.e.). 



In the vegetable kingdom hypoxanthine occurs 
in beer yeast (Sohutzenberger, Chem. Zentr. 
1877, 73) ; potato juice to the extent of 0-0037 
gram per 1 c.o. (Sohulze, Landw. Versuchs. Stat. 
1882, 28, 111) ; in the leaf buds of plane and 
maple, bark of plane, in lupines, young gra^s, 
red clover, oats, vetch, and in sugar beet 
(Sohulze and Bosshard, Zeitsch. physiol. Chem. 
1885, 9, 420; Von Lippmann, Ber. 1896, 29, 
2645). 

The chief source of hsrpoxanthine in the 
animal economy appears to be nucleic acid, 
which, under the action of certain tissue enzymes ; 
most abundant in the liver and spleen, is decom- 
posed ; thus nuclease liberates the purine bases 
adenine and guanine, and .these are further 
changed by the deamidising enzymes adenase 
or guanase into hypoxanthine and xanthine 
respectively, and finally oxydases convert 
hypoxantmne into xanthine and xanthine into 
uric acid (Halliburton, Chem. Soc. Reports. 1909, 
168). Salomon (Ber. 1887, 11, 674; 12, 
96) obtaiiied hypoxanthine from blood fibrin 
by the action of pancreas ferment, by simpla 
decay, or by digestion with dilute hydrochloric 
acid (8 parts in 1000 parts of water) ; and 
Kossel (Zeitsch. physiol. Chem. 1881, 6, 152) 
found that the nuclein from pus cells and goose 
blood yielded on prolonged boiling 1-03 and 
2-64 p.o. respectively of hypoxanthine. On the 
other hand, Leathes (J. Physiol. 1906, 35, 126, 
206), Leonard and Jones (J. Biol. Chem. 1909, 
6, 453), and Vogtlin and Jones (Zeitsch. physiol. 
Chem. 1910, 66, 250), have shown that uric acid 
excretioli is related in some way to muscular 
exercise, and the most important purine base 
which contributes to the endogenous uric acid 
is muscular preformed hypoxanthine. This is 
not directly connected with nuclein metabolism, 
since it may occur in the absence of adenase, 
an essential factor in the passage from nucleic 
acid to hypoxanthine. 

Fischer (Ber. 1897, 30, 2226 ; D. R. P. 1898, 
17673) has synthesised hjrpoxanthine from 
trichloropurine by the following reactions: 
trichloropurine when heated with normal aqueous 
potassium hydroxide yields 6-oxy-2 : S-dichloro- 

NH-CO-C-NH\ 
purine I 11 ^CQ, which is reduced' 

Ca:N— C— N<^ 
to hypoxanthine by the action of hydrogen 
iodide. Hypoxanthine is also obtained from 
adenine {6-aminopurine) by the action of 
nitrous acid, or from uric acid by reduction with 
alkali and chloroform (Sundvik, Zeitsch. physiol. 
Chem. 1897, 23, 476 ; 26, 13). 

A further synthesis of hypoxanthine from 
ethylcyanacetate and thiourea is described by 
Traube (Annalen, 1904, 331, 64) ; i-amino-Q- 

NH-CO-CH, 
hydroxyVi-fhiopyrimidine | j obtained 

CS-NH-C:NH 
by the condensation of ethylcyanacetate and 
thiourea in the presence of sodium ethoxide, 

NH-CO-C : NOH 
forms an iaonitroso derivative | ^ | 

CS-NH-0:NH 
which on reduction yields 4 : 5-diamino-G-oxy- 

NH-CO-C-NHj 
2-thiopyrimidine I 11 • When the 

CS-NH-C-NHj 
sodium salt of the formyl derivative of this 



HYPOXANTHINE OR SARCINE. 



eompound is heated at 260°-255° it is converted 

NH-CO-C-NHv 
into 6-oi!y-2-thiopunne 1 || '^CH.wMch 

CS-NH-C— N^ 
loses its sulphur on treatment with dilute nitric 
acid (25 p.o.) at 100°, yielding hypoxanthine 
NH-CO'C-NH. 
I 11 >CH. 

Hypoxanthine is a white crystalline powder, 
crystallising in two modifications, one form 
consisting of needles containing water Of crystal- 
lisation, which spontaneously and readily lose 
their water yielding anhydrous octahedra 
(Micko, Zeitsch. Nahr. Genussm. 1904, 8, 225) ; 
it decomposes without melting at ISO", and 
dissolves in 69-5 parts of boiling water or 1400 
parts at 19° (Fischer, Ber. 1897, 30, 2226). 

Hypoxanthine exhibits both acid and basic 
properties, and combines with one equivalent of 
ah acid, or two equivalents of a base ; the 
following salts are described : the hydrochloride 
CjHiNiO'HCljHaO, crystalline plates or needles, 
yields a sparingly soluble platinichloride 

(C6H,N40-HCl),.PtCa«; 
and a crystalline aurichloride 

ajH^NjO-Ha-Auaj 

the hydrobromide CsHjNiO-HBr and nitrate 
CsHjNjO'NHOa are crystalline ; the picrate 
dissolves in 450-500 parts of water at the 
ordinary temperature (Klriiger and Salomon, 
Zeitsch. physiol. Chem. 1898, 26, 362). The 
bariiim derivative CBH4N40-Ba(OH)2 is crystal- 
line, the silver salt C5H2NiOAg2,H20 loses 
JHjO at 100° ; in the presence of excess of 
ammonia the salt crystallises with 3H2O, and 
loses 2iH20 at 120°. 

Hypoxanthine forms characteristic sparingly 
soluble derivatives with certain metalUo salts, 
and these are used for separating and estimating 
the base. The compour^ with mercuric chloride 
CjHaNiO.HgCla.HjO is crystalline ; the com- 
pound with silver nitrate CjHjNjO.AgNOs is a 
flocculent precipitate, crystallising from hot 
nitric acid (sp.gr. 1-1), 1 part dissolves in 4960 
parts cold nitric acidj according to Salkowski 



(Pfliiger's Archiv. 4, 91), the presence of gelatin 
prevents the precipitation of hypoxanthine by 
silver nitrate; the picrate AgCjH,N40,C,H,N,0, 
is a lemon-yellow crystalline salt, insoluble in 
cold water, precipitated from a hypoxanthine 
salt by Bomum picrate and silver nitrate 
(Bruhns, Zeitsch. physiol. Chem. 1890, 14, 555). 

Bromohypoxanthine CBH3BrN40,2H40 is 
sparingly soluble in cold water, and is obtained 
by the action of bromine (1 mol.) on hypoxan- 
thine (1 mol.) at 120°, or by the action of sodium 
nitrite on a solution of bromadenine at 70°; 
on heating hypoxanthine for 6 hours at 100°- 
150° with excess of bromine, bromohypoxanthine- 
tetrabromide hydrobromide C5H3BrN40-HBr-Bri 
is obtained (Kriiger, Zeitsch. physiol. Chem. 
1894, 18, 449). 

Urethane of hypoxanthine CjHaNjP-COOEt 
prepared by the interaction of ethylchloro- 
carbonate and hypoxanthine, crystallises in 
plates, m.p. 185°-190°, and is sparingly soluble 
(Bruhns and Kossel, Zeitsch. physiol. Clwm. 1892, 
16, 1). Hypoxanthine combines with adenine 
to form the crystalline compound 

(Bruhns, Ber. 1890, 23, 225) ; and like other 
purine derivatives containing an imino group 
in position 7 it yields coloured derivatives with 
diazobenzene salts (Burian, Ber. 1904, 37, 696). 

Separation and estimation. — ^From mixtures 
of the xanthine"bases, adenine and hypoxanthine 
are separated from xanthine and guanine by 
means of their sparingly soluble derivatives with 
silver nitrate in nitric acid solution. The mixed 
silver compounds are decomposed by hydro- 
chloric acid, the filtrate nearly neutraUsed with 
sodium carbonate and the adenine precipitated 
as picrate. The filtrate is neutralised with 
ammonia, and the hypoxanthine precipitated 
with ammoniacal silver nitrate (Bruhns, Ber. 
1890, 23, 225; cp. also Kossel, Zeitsch. physiol. 
Chem. 1883, 8, 404 ; Schindler. ibid. 1889, 13, 
432 : Kriiger, ibid. 1894, tO, 170). M. A. W. 

HYRGOL V. Synthetic dkttgs. 

HYSTARAZIN t>. Alizabin aud allied 

COLOUBIKG MATTERS. 



IBIT V. Synthetio dettos. 

IBOGA. A plant Tabernanthe iboga (Baill.), 
natural order Acanthacece, found in the Congo, 
the root of which is chewed by the natives and 
which is said to possess properties similar to 
those of coca and kola. It enables persons to 
withstand fatigue, is used as a renj)tdy for 
sleeping sickness and acts as an aphrodisiac. 
According to Dybowski and Landrin, its active 
principle is an alkaloid, ibogalne CaoHjjNaO, 
which readily oxidises on exposure to air. It 
is Isevorotatory and forms weU crystallised salts 
(Compt. rend. 133, 748). 

ICACIN V. Oleo-besins. 

ICE BLACK V. Azo- colofbiho mattebs. 

ICELAND-SPAR v. Calcitb; Calcium. 

ICE-SPAR V. Cbtolite. 

ICHTHARGAN v. Synthetic sbuqs. 



ICHTHYOL. A pharmaceutical product dis- 
tilled from fossilised fish remains, found in the 
Tyrol and on the coasts of the Adriatic. 

Crude ichthyol from the Seefeld district 
between Southern Bavaria and the Tyrol has 
long been used as an antiseptic remedy. The 
crude ' rock oil ' is obtained by simple distilla- 
tion from the shale or ' stinkstein,' a bituminous 
substance of a grey or black colour occurring 
in the upper dolomites. The amount of oil ob- 
tained varies from 1 to 10 p.o. An installation 
of nine stills yields, on an average, 15 to 20 kUos. 
of oil per charge. In one wor& the output of 
crude oil is over 3000 kUos per annum. As 
found in pharmacy, the substance consists 
mainly of the ammonium Bulphonate. It is 
not a simple substance but a mixture of am- 
monium ichthyol sulphonate with about 1 p.o. 



INDAMINES AND INDOPHENOLS. 



93 



of a powerful-smelling empyreumatio oil, 6 to 
7 p.o. of ammonium sulphate, and about 60 p.o. 
water. 

According to Eaumann and Schotten, 
ichthyol-sulphonic acid has the formula 
CaaHjeS(SOjOH)j. 

An odourless ichthyol has been prepared by 
Knorr & Co. which has the therapeutic activity 
of the original sjrong-smelling product (J. See. 
Chem. Ind. 1903, 1304 ; 1910, 44, 174, 264). 

For ichthyol preparations v. SynShbtio 

DETTGS. 

ICICA and ICAGIN v. Qleo-besins. 

ICOSANE CjoH^a. A hydrocarbon found in 
paraffin. M.p. 36°; b.p. (under 15 mm. pressure) 
205°; sp.gr. 0-778 at 37°/4°. Formed by the 
action of sodium on normal decyl iodide. 

ICOSONENE V. Bbsin oil. 

lORYL V. Eltjobanthenb. 

IGNOTINE V. CABNOsmB. 

njCIC and lUCYLIC ALCOHOLS v. Bird- 
limb. 

ILLIPE-NOT FAT. lUipe'-nuts yield a con- 
siderable quantity of a fat which is imported 
from the Dutch East Indies, and used in con- 
junction with palm-kernel oil in the manu- 
facture of candles. It is_ weU adapted for the 
saponification method of stearin manufacture. 
In the autoclave it yields about 10 p.c. of 
glycerol of 28°B. (J. Soo. Chem. Ind. 1898, 161, 
358) ; V. Bassia oil. 

ILMENITE, oi titaniferous iron-ore. A 
common mineral with approximately the 
formula FeTiOg, but of variable composition. 
In its ihombohedral crystalline form it shows a 
close agreement with haematite, and it has 
consequently, until recently, been regarded as 
an isomorphous mixture of ferric oxide and 
titanium sesquioxide, the formula being written 
as an oxide (Fe,Ti)20|. The discovery of the 
rhombohedral titanates of magnesium and 
manganese, geikielite (MgTiOa) and pyrophanite 
(MnTiOj), and the frequent presence of mag- 
nesium (and manganese) in Umenite, suggest, 
however, that the mineral is really a titanate of 
ferrous iron, FeTiO, (S. L. Penfield, Amer. J. 
Sci. 1897, 4, 108). In the variety picroilmenite 
a considerable amount of irpn is replaced by mag- 
nesium, the formula then being (Fe,Mg)Ti03 (T. 
Crook and B. M. Jones, Min. Mag. 1906, 14, 165). 

nmenite ia black with a sub-metallic lustre, 
and often a smooth and lustrous conchoidal 
fracture, Bp.gr. 4-5-6; H. 6-6. The massive 
mineral in appearance somewhat resembles 
magnetite, from which it is readily distinguished 
by its feeble magnetic character. It is of con- 
stant occurrence as isolated grains in the more 
basic igneous rocks (gabbio, diabase, basalt, 
&c.); and in certain instances it forms rich 
segregations in such rocks. Enormous deposits 
of Hmenite are found under these conditions at 
several places in Norway, Sweden, Canada, and 
the United States. With the weathering and 
breaking down of these igneous rocks, grains of 
jlmenite {Manaccanite, from Manaccan in Corn- 
wall) collect in the beds of streams, sometimes 
forming considerable deposits of ' black iron- 
Sand.' 

Although large deposits of ilmenite are 
available f6i mining, the mineral has not yet 
found any important applications. It has been 
used tot the preparation of titanium paints and 



enamels ; and in the future it may be more 
utilised for the manufacture of titanium-steel, 
which possesses great ductility and a high limit 
of elasticity. L. J. S. 

IMPERIALINE CasHjoNO,. An alkaloid dis- 
covered by K. Fragner in Fritillaria Imperialia 
(Linn.). It is a heart-poison, and is probably 
closely related to the older alkaloid TuUpine, dis- 
covered by Gerard in TuUpa Qesneriana (Linn.). 

IMPERIAL GREEN. EmeraU Green v. PiQ- 

MENTS. 

IMPERIAL SCARLET n. Azo- colottrinq 

MATTERS. 

IMPERIAL YELLOW v. Aubantia. 

INACTIVE CAMPHOR v. Camphoks. 

INCANDESCENT MANTLES ». Gas mantles. 

INCARNATRIN v. Gltjcosides. 

INCENSE TREE RESINS v. Gum-rbsins; 
Oleo-kesins. 

INDALIZARINE v. Oxazine colottring 
matters. 

INDAMINES and INDOPHENOLS. 

Constitution and mode o/ formation. — The 
indamines and indophenols are colouring matters 
most of which are too unstable to be of great 
practical value, but many of them are interesting 
as intermediate products in the manufacture of , 
other more important dyestuffs. From a 
theoretical point of view they can claim great 
importance, as they form the starting-p 'int of 
the modern ' quinonoid ' structural f ormulse now 
universally adopted for the majority of colouring 
matters. This is due to the fact that the inda- 
mines and indophenols are the simplest real 
colouring matters derived from the quinoues, 
which are now considered as prototypes of 
chromogens. 

AH aromatic hydrocarbons are capable of 
forming quinonoid derivatives by the displace- 
ment of 2 hydrogen atoms by 2 atoms of 
oxygen. These may stand either in o- or in p- 
position to each other, whilst no quinones have 
ever been discovered which contain the oxygen 
atoms in m- position. The divalent nature 
of oxygen forces us to consider the quinones 
either as peroxides of aromatic hydrocarbons 
OI as alicyclic diketones. The first of these 
possibilities was formerly considered as more 
probable and was made the basis of this' 
article in the first edition of this dictionary. 
Since then the diketone formula has come to be 
generally adopted and it wiU therefore have to 
be used in this revlsion.of the article. 

The following formulae represent the two 
different constitutions which may be given to 
})-quinone, the prototype of all the substances 
to be mentioned in this article: 

O 

Q 

o— 

Peroxide formula. Diketone formula. 

AH other quinones, no matter from what 
aromatic hydrocarbon they are derived and 
whether they belong to the o- or p- series, 
may be similarly formulated and neither of 
these two different constitutions can be claimed 
as undoubtedly preferable to the other. It is 
very probable that the quinones are tautomeric 



H 



INDAMINES AND INDOPHENOLS. 



Y 



and possessed of both constitutions according to 
th') cironmstances under which they react. 

If the oxygen of p-quinone be replaced by 
divalent imino groups =NH, two compounds 
may be obtained, p-quinoneimide and p- 
quiuonediimide, which for many years have been 
considered as hypothetical but have recently 
been prepared by Willstatter (Ber. 37, 1494, 
4605). They are very unstable substances the 
constitution of which is expressed by the follow- 
ing formulas (based, as aU the subsequent 
formulae of this article, on the diketonic con- 
stitution of the quinones) 

O N— H 

II 



iir— H N— H . 

2>-Quinoneimide. y-Quinonediimide. 

The iminic hydrogen of these compounds may 
be replaced by halogen atoms, and we thus obtain 
substances of a comparatively stable nature 
which have been kaown for a long time and may 
be used for the preparation of various deriva- 
tives. It was by treating quinonedichlorodi- 
imide, dissolved in ether, absolutely free from 
moisture, with the theoretical quantity of dry 
hydrogen chloride that Willstatter first suc- 
ceeded in preparing i)-quinonediimide. Later 
on he found a general method for the production 
of both these imides in the oxidation of either 
2)-phenyIenediamine or p-aminophenol with dry 
silver oxide. They are slightly basic sub- 
stances, capable of forming unstable hydro- 
chlorides. In a free state they are white, but 
they resemble quinone in their reactions. Their 
great tendency to polymerisation is the cause why 
previous attempts at their isolation have failed. 

Qulnonechlorolmide C.H- has been obtained 
II 

O 
by Schmitt and Bennewitz (J. pr. Chem. [ii.] 
8, 2). it is prepared by allowing a solution' of 
43 grams 2>-aminophenol hydrochloride In 500 
CO. water and 100' c.c. concentrated hydro- 
chloric acid to flow into a solution of sodium 
hypochlorite prepared by introducing 35 grams 
of chlorine into an ice-cold solution of 46 
grams sodium hydroxide. The imide settlfes 
oTlt and may be recrystaUised from light 
petroleum (WiUstattop, Ber. 37, 1499). It 
forms yellow crystals, ' melting at 85°; it is 
slightly explosive, volatile with aqueoua yapour, 
and resembles quinone in many of its properties. 

N-Cl 

Trichloroqainoneehloroimide OjHa. is 

II 

prepared m the same manner from triohlor- 
aminophenol hydrochloride (Schmitt and Andre- 
sen, J. pr. Chem. [ii.] 23, 438 ; 24, 429). YeUow 
needles, m.p. 118°, similar to quinoueohloromide 

Dlbromoqulnonechloroimide CgHjiBr, is 

II 
O 



obtained by adding a solution of bleaching- 
powder to an aqueous acidulated solution of 
the double salt of dibromaminophenol hydro- 
chloride and tin chloride. It separates in 
flesh-coloured crystals, melting at 80° (R. 
Mohlau, Ber. 16, 2845). 

N-a 

II 
Quinonedichlorodiimide CsH^ is formed 

II 

. N.a 

by acting with a solution of bleaching-powdei 
upon a solution of })-phenylenediamine 
hydrochloride (Krause, Ber. 12, 47). Will- 
statter (Ber. 37, 1498) prepares it by allowing a 
solution of 64 grams p-phenylenediamine 
hydrochloride in 120 c.c. hydrochloric acid and 
600 c.c. water to flow into a hypochlorite solu- 
tion prepared by introducing 76 grams of chlorine 
into the solution of 90 grams sodium hydroxide 
in 600 C.C. of water. The imide separates in 
whitish flakes and may be recrystaUised from 
light petroleum. White needles, insoluble in 
water, soluble in alcohol, benzene, &c., and 
exploding at 126°. 

N-Br 

Quinonedibromodiimlde CgH. may be pre- 

II 

N-Bi 
pared by acting with bromine water upon p- 
phenylenediamine hydrochloride (Krause, Ber. 
12, 60). It is similar to the chloro derivative, 
and explodes at 86°. 

These substance's are not colouring matters, 
as may be seen from the above description. 
They cannot be colouring matters, because they 
are indifierent, whilst every dyestufl must be 
either an amine or a phenol (Witt, Bau und 
Bildung farbendei Kohlenstoffverbindungen, 
Ber. 9, 522). Their ohromophorio character, 
however, becomes apparent in those of their 
derivatives which are endowed with either 
basic or acid properties. NitrosodimethylanUine 
and nitrosophenol, which, as their constitutional 
formulas show, are closely related to quinonedi- 
imide and quinoneimide : 

N-H l^-CH, 

" II ii^ca 





N— H 
Quinonedlimlde. 



N— H 



Q 

N— OH 

Qulnonedimethylamlno- 
oxime chloride (Nitroso- 
dlmethylaniline hydro- 
chloride). 

N— OH 



9 Q 

o O 

Qulnonetmlde. Qnlnoneoxime (Nitrosophenol). 
are by_ virtue of their basic and phenolic nature, 
colouring matters possessing some affinity for 
fibres, although they have no practical value as 
dyestuffs. 

We may, however, obtain real colouring 
matters, many of which have proved useful and 



INDAMINES AND INDOPHENOLS. 



interesting, by preparing substitution products of- 
the quinoneimides in which the substituting 
radicle is attached to nitrogen. Such products 
may be prepared by acting with amines or 
phenols.upon quinoneimides, or their equivalents, 
quinonamidoximes (nitroso bases) and quino- 
neozimes (nitrosophenols). Various cases may 
here be cited : 

1. By acting with aromatic amines upon 
quinonedichlorodiimides, indamines are formed, 
thus : 



N— a 

II 

A, 



N— a 



I 



Ha+ {^ 



N— a NH, 

Diotiloroguinone- a-Naphthylamine. 
diimide. 



N 

C]oHj-NHj 
Naphthindaimne. 

2. By acting with aromatic amines upon 
quinone-amidbximes (nitroso bases) indamines 
are formed likewise : 

/CH3 
/CH3 



N— ( 



/ 



//- 
/CH, 

IJ-^Cl NH, * O.H, 

/\ \/\ I 

II II+ 1 |=H,0+ N 

II f HaH,N\/\ 

N— OH NH2 II II 

Nitrosodimethyl- m-Tolylene- \/"^CH3 

aniline hydro- diamine. 11 

cbloride, Jirrr 

(Dimethylaminoquinoneoxime -"^ 

cbloride.) Tolylene blue. 

In this case, as in many similar ones in this 
group, the quinonoid character may in the forma- 
tion of the dyestuff be shifted from one benzene 
ring to the other. This has been indicated in 
the formula, although we have no positive proof 
that such shifting takes place in the formation 
of tolylene blue. 

3. By acting with aromatic amines upon 
quinoneohloroimides normal indophenols are 
formed : 



Na I '■ 

II CaHj O.HCa, 

C,Ha, + 1 =HC1+ II 

11 N(CH3)j N 

Dimetbyl- | 

anlUne. C,H4N(CH3)a 

Blmetbyltricliloro- 
benzindopbenol. 

4. By acting with phenols upon qninone- 
dichlorodiimides indophenols of a more compli- 
cated nature may be formed : 

N— a N— CsHj-OH 

II II 

C,H4 + 2C.H5OH = 2Ha + C.H, 
II Fbenol. || 

N-a N— CeH^-OH 

Qninonedicblorodiimide. Complex indophenol. 

6. By acting with phenols upon quinon- 
amidoximes (nitroso bases) normal indophenols 
are formed : 





Triehloro- 
guinone- 
chloioimide. 



/CHj 
N^CH, 

II Ca -fC,„H,-ONa=HaO+NaCl+N 
CjH, Sodium a- 

II naphtboxide. 

N— OH 

Nitrosodi- 

metbylaniline 

hydrOohlorlde. 



95 

N(CH,), 

OeH, 

I 



(X) 



O 

Normal naphthlndopbenol. 
In this case again, as in No. 2, a migration 
takes place and the quinonoid nature is shifted 
from the benzene to the naphthalene nucleus. 
This can be proved to be the case by the fact that 
the resulting dyestuff is a weak base but entirely 
devoid of phenolic properties. It cannot there- 
fore contain an OH group. 

6. By acting with phenols upon quinone- 
chloroimides colouring matters are formed, which 
although practically belonging to the indophenols 
are distinguished by the presence of a free 
hydroxyl group, by which they assume phenolic 
properties, dissolve in alkaUs and have therefore 
been designated by the name of ' acid indo- 
phenols.' 

NCr 

II II 

C„H,+CeH50H=HCl+GA 

II II 

O N 

CcH^-OH 
Quinone chloioimlde. Acid indophenol, solubleln alkalisi 

7. The same result takes place if the equiva- 
lents of quinoneimide, viz. the quinoneoximes or 
nitrosophenols be acted upon with phenols : 







II 



CjH, 



0eHj+0sH3OH=H,O+N 

II I 

NOH CsH.OH 

Qulnoneoxime Phenol. Acid indophenol, soluble 
(nitrosopbenol). In allsalis. 

8. If, however, amines be acted upon with 
nitrosophenols, a normal indophenol is the 
result : 


II 
O C.H, 

II 1: 

06Hj-)-Ci„H,-NHj=HaO-fN 

II I 

N— OH C,„H,-NHa 

Nitrosopbenol. o-Naphthyl- Indophenol, insoluble 
amine. in alkali. 

9. The quinones themselves may be utilised for 
the production of these dyestufEs by being acted 
upon with suitable diamines or amiubphenols : 

O NHj O 

II I II 

Ci„H,+C,H4=H,0+Cj„H, 

II I I! 

NHj N 

6.H. 



Napbtha- 
quinone. 



j)-Phenylene- 
diamine. 



NH2 
Indophenol. 



INDAMINBS AND INDOPHENOLS. 



This reaction makes it evident that the 
indamines and indophenols are nothing else 
than a certain group of the larger family of 
quinone anilides, viz. those of these anilidea 
which contain-the auxoohromic groups necessary 
for developing their nature as dyestuffs. 

Foe the production of indamines and indo- 
phenols it is, however, not necessary to start 
from ready-formed quinones, quinoneimides, 
diimides, or quinoueoximes. It is possible to 
prepare these substances by the joint oxidation 
of amines or phenols with compounds which are 
capable of producing a quinoneimide or diimide. 

In this process we may assume that the 
hypothetical quinoneimides and -diimides are 
formed as intermediate products which imme- 
diately react upon the amines or phenols pre- 
sent in the mixture, forming indamines or indo- 
phenols, as -the case may be. Every- j)-amino- 
phenol or ji-diamine is capable mi being used 
for this reaction, and a large variety of colouring- 
matters may thus be produced. The following 
combinations may tako place : 

10. j)-Diamines simultaneously oxidised 
with aromatic amines give rise to the formation 
of indamines. jjjj 

NH, II 

+ 1 I +20=2HjO+N 

UH, C.HjNHa 

NH, I 

p-Phenylene- m-Phenylene- NH, 

diamine. diamine. Indamine 

, (phenylene-violet) . 

11. ji-Diamines oxidised with aromatic 
phenols produce normal indophenols : 

NH, 






Y 



NH, 

c;Hj+0„HjOH-f-20=2H,0-i-N 
NHj Phenol. Jl 

p-Phenylene- C, 



sH^i 



diamine. 



ioH, 



O 



Typical indophenol. 
12. j}-Aminopbenols oxidised with aromatic 
amines produce normal indophenols : 

N(CH,), 



-.OH 



OjH, 



OeHi -J-C.H5N(CH,)a+20=2HjO+N 
~-^jTTT Dimethylaniline. || 

}>-Amino- Y' * 

plienol. 11 

Indophenol. 
13. j)-Aminophenols oxidised with aromatic 
phenols produce acid indophenols : 

« OH 



CfoH, 



OH 



CeH, 



+0aH6OH-f2O=2HjO+N 
^NH, ^''«"°'- ^ 1„ 

j)-Amlno- V' * 

phenol. II 

O 
Acid indophenol. 



From the above it will be seen that all the 
various oplourmg matters prepared by these re- 
actions and built up on the quinone type may 
be subdivided into three varieties : — 

a. True indamines containing no oxygen, 
and having the generic formula : 
Eii=NH 



I 



Rii -NHj 

strong bases, forming stable salts with mineral 
acids. 

6. Normal indophenols, containing oxygen 
in their chromophoric group, being amino 
derivatives of substituted quinoneimides of the 
generic formula : 

Rn=0 

Rn -NHj 
very weak bases, incapable of forming stable 
salts. With these the hydroxy derivatives of 
quinonediimides : 

Rii— OH 



N 



Eii=NH 
are practically identical, being transformed into 
normal indophenols in statu nascendi by the 
shifting or migrating process already mentioned. 
c. Acid indophenols, hydroxyl derivatives of 
quinonimides of the generic formula : 

Rn=0 



N 



RH-OH 

distinct phenols, dissolving in caustic alkali 
solutions with intense colourations. 

Like all colouring matters the indamines 
and indophenols are capable of being reduced 
by the action of nascent hydrogen, of which two 
atoms are taken up. Culourless ' leuco- ' com- 
pounds are formed which stand in the same 
relation to the original dyestuff as hydro- 
quinone stands to quinone : 

fen-NH. Rii-NH, Rn-OH 



NH 



NH 



I 
NH 



Rn-NH, Rn.OH Rn-OH- 

Leuco-indamine. Normal Acid 

leuco-indophenol. leuco-indophenol. 
It will be clearly seen that these formulsa of 
the leuco derivatives ate identical with the 
formulae of paradiamino, aminohydroxy, and p- 
dihydroxy derivatives of secondary aromatic 
bases. Nowastheleuco derivatives of indamines 
and indophenols are capable of reoxidation into 
the original dyestufi, it is apparent that we 
have by this means three additional methods for 
the production of such colouring matters : 

14. Di-j3-amino derivatives of secondary 
aromatic bases may be oxidised into indamines. 

15. p-Amino-p-hydroxy derivatives of 
secondary aromatic bases may be oxidised into 
normal indophenols. 



INDAMINES AND INDOPHENOLS. 



07 



16. Di-p-hydroxy derivatives of secondary 
aromatio bases may be oxidised into acid indo- 
phenols. 

The c();iditions under which these various 
reactions should be performed are stated below. 

The remarkable relations existing between 
dyestuSs and their leuco oompounds were 
recognised and studied by' chemists at an early 
period. In no group are they so clearly defined 
as in that of the indamines and indophenols. 
Their complete elucidation in this group very 
naturally sheds light upon analogous phenomena 
observed in other colouring matters and thus 
the study of this class of substances greatly 
facilitated the introduction of the modern views 
of the ' quinonoid ' constitution of colouring 
matters. 

Literature on the Constitution of Indamines 
and Indophenols, Otto N. Witt, J. Soc. Chem. 
Ind. 18S2, 255 ; R. Mohlau, Ber. 16, 2843 ; Otto 
N. Witt, British Association, 1887 ; Journ. Soc. 
Dy. Col. 1887; R. Nietzki, Organische Farb- 
stoffe, 6th ed. 1906, 197 et seq. 

History. — The first indamine observed was 
the intermediate product obtained in the pro- 
duction of safranine, of which, however, no 
account was published. In 1879, Otto N. Witt 
prepared the first indamine in a state of purity 
by acting with nitrosodimethylaniline hydro- 
chloride upon m-tolylenediamine (Ber. 12, 
931 ; Chem. Soc. Trans. 1879, 1, 356). In 1881, 
Otto N. Witt and Horace Eochlin obtained 
patents for the production of normal indo- 
phenols. ' The production of ' acid indophenols ' 
by the reaction of quinonechloroimide upon 
phenol was first mentioned by Hirsch (Ber. 13, 
1909), and discussed by Mohlau (ibid. 16, 2845). 
The normal indophenols only have found a 
practical application in dyeing and calico- 
printing. Owing, however, to their insufficient 
resistance to the action of acids and to the 
difficulties in their application, they did not 
make very rapid progress in the favour of 
practical dyers and colourists. A change for 
the better took place, when it was shown that 
the typical indophenol is a good vat-dye and 
capable of being used in combination with 
indigo. The consumption of indophenol became 
considerable for a while, but went down again as 
rapidly as it had gone up when the introduction 
of synthetic indigo lowered the prices of this 
' king of dyestuffs ' and the invention of many 
indigoid colouring matters overwhelmed the 
dyer with dyes suitable for the vat-process. 

In later years some of the indophenols have 
become important as raw materials for the pro- 
duction of some valuable sulphur dyes, which 
are prepared from them by the well-known pro- 
cess of boiling or melting with alkaline sulphides. 
This new application of the indophenols had 
been first indicated in D. R. P. 132212 of the 
Gesellschaft fiir Chemische Industrie, in Basle 
(14 Deo. 1898), and the corresponding Fr. Pat. 
284387 and Amer. Pat. 665547. 

Properiiea. — ^The properties of the indamines 
and indophenols are more uniform than those of 
other classes of colouring matters. It has con- 
sequently been necessary to prepare only a small 
number from the host of possible members of 
this group in order to obtain a fair notion of the 
properties of the whole group. With very few 
exceptions their shade is blue or violet ; in some 
Vol. III.— T. 



oases a bluish-green. The shade of the dye- 
stuff is exhibited : 

a. In the indamine group by the normal salts 
of the indamine bases. 

b. In the group of normal indophenols by 
the free bases. 

c. In the group of acid indophenols by the 
alkaline salta of the dyestufis. 

All the indamines and indophenols possess 
the generic character of the quinone group. 
They are therefore capable of acting as oxidising 
agents if brought together with oxidisable sub- 
stances. In such reactions they take up hydro- 
gen and are transformed into their leuco deri- 
vatives. So considerable is their tendency to 
act as oxidising agents that, under suitable con- 
ditions, an indamine or indophenol will attack 
its own molecules, when a mixture of its oxida- 
tion products and its leuco compounds is the 
result {v. Safranines, art. Azinbs). The con- 
ditions under which such reactions take place 
are, an elevated temperature and the presence 
of mineral acids. The indamines and indo- 
phenols are consequently unstable in the 
presence of acids, whilst in alkaline and neutral 
solution they display but little tendency to de- 
compose. 'A similar decomposition is caused, 
especially in the indamines, by the action of 
sunlight ; the normal indophenols may, on the 
contrary, be called rather fast. > 

The following is an account of those members 
of this group of dyestuffs which have been more 
closely examined or proved important from a 
technical point of view : — 

I. iNSAMmss. 
Phenylene-blue CuHnNs 

Constitution CjH,— NH, 
I 

N 
II 
C,Hi=NH 

This compound is best prepared by oxidising 
a mixture of jj-phenylenediamine and aniline 
hydrochloride in equal molecules in the cold, 
with the theoretical quantity of potassium dichro- 
mate. A greenish-blue liquid is formed, from 
which the iodide of phenylene-blue may be pre- 
cipitated by the addition of potassium iodide 
solution. This salt forms long needles with a 
green metallio luWe. It is soluble in water with 
a greenish-blue colour, which turns into green on 
the addition of mineral acids. Acid solutions 
decompose very rapidly, a considerable quantity 
of j)quinone being formed in this decom- 
position. On reduction phenylene-blue yields 
di-p-aminodiphenylamine, from which phenyl- 
ene-blue may be regenerated by simple oxida- 
tion. Phenylene-blue is transformed into saf- 
ranine on being boiled in a neutral solution with 
aniline hydrochloride {v. Safranine). 

Literature.— R. Nietzki, Ber. 1883, 16, 464 ; 
R. Nietzki, Organ. Farbstoffe, 5th ed. 1906, 200. 

Tetramethyl derivative of Phenylene-blue 
(Dimethylphenylene-green). 

CieHjoNja. Constitution C.H,— N<^^'' 

N 

II .^H, 

C,H4=NCH3 

^Cl 



98 



This interesting compound, which is the 
completely methylated derivative of the pre- 
ceding one, is formed by the joint oxidation 
of os^-dimethyl-p-phenylenediamine w|th 
dimethylaniline, in equw molecules, •mth 
potassium dichromate in the presence of zinc 
chloride {Bindschedler, Ber. 13, 207). The zinc 
double salt is at once dejiosited from the liquid. 
According to the quantity of zinc chloride pre- 
sent the crystals are either of a copper colour or 
have a metaJlio green lustre. These crystals 
are freely soluble in pure water, with a fine 
green colouration. Potassium iodide precipitates 
from this solution the phenylene-green iodide 
CieHjjNjI in beautiful green needles, which are 
easily soluble in pure water, very insoluble in 
the presence of an excess of potassium iodide. 
The platinum double chloride has the com- 
position (CisHjoNjaiaPta^; dimethylphenyl- 
ene-green is more stable than the majority of 
indamines. On reduction it yields tetramethyl ■ 
diaminodiphenylamine from which the green, 
may be regenerated by oxidation. 

Dimethylphenylene-green dyes silk and other 
fibres a yellowish shade of green. It has, how- 
ever, found no application as a colouring matter, 
being rather unstable to light. 

Its solution, on being boiled with the solu-' 
tion of an equal molecule of the hydrochloride 
of a primary amine, yields the corresponding 
safranine. (Also Safranine.) 

Literature. — Bindschedler, Ber. 13, 207 ; E. 
Nietzki, ibid. 16, 464 ; Bindschedler, ibid. 16, 865. 

biethylphenylene-green CsoHagN.Cl is ob- 
tained by oxidising diethyl-jj-phenylenediamine 
with diethylaniline in the presence of mercuric 
chloride. Very similar to the methyl derivative, 
but less stable. 
' Literature. — Bindschedler, Ber. 16, 867. 

Homologues of phenylene-blue. These are 
formed by the joint oxidation of p-phenylene- 
diamine and the homologues of aniline or of 
})-tolylenediamine with aniline and its homo- 
logues. They play an important part in the 
manufacture of the commercial safranines, in 
which they are obtaiaedasintermediate products. 

Literature. — 0. N. Witt, J. Soo. Chem. Ind. 
1882 256 

Witt's' phenylene- Violet CijHyN^-Ha. This 
substance is obtained by the joint oxidation 
of })-phenylenediamine . with m-phenylene- 
diamine. Its aqueous solution, which exhibits 
a fine purple shade, is decomposed on boiling, 
when a corresponding diamino-azine or eurho- 
dine is formed. Similar compounds are obtained 
by the joint oxidation of other ^-diamines 
with m-phenylenediamine. This reaction is, 
therefore, applicable as a test for both p- and' 
m-diamines. 

Witt's phenylene-blue C,4H„NiEa. The 
dimethyl derivative of the preceding substance 
is formed either by the joint oxidation of 
dimethyl-p-phenylenediamine and m-phenylene- 
diamine hydrochloride, or by mixing together 
lukewarm solutions of nitrosodimethylaniUne 
hydrochloride and m-phenylenediamine, both 
dissolved in glacial acetic acid. It forms bronze- 
coloured crystals, readily soluble in water, with 
a purplish-blue shade. On the addition of 
mineral acids unstable diacid salts of a yellowish- 
brown colour are formed. The aqueous solution 
is decomposed by prolonged boiling, yielding 



INDAMINES AND INDOPHENOLS. 

neutral violet, a colouring matter of the eurho- 
dine croup (v. Safranine). _ 

iacratere.— Otto N. Witt, D. K. P. 15272, 
1880 ; Eng. Pat. 4846, 1880. 

Tolylene-Mue CjsHisNi-Ha 

<CH3 
•na 



H 



N 
.N-i, 



Hj-CH,, 



NH 



This is the most thoroughly investigated 
member of the group. It is formed by the action 
of oxidising agents upon a mixture of dimethyl- 
j)-phenylenediamine and m-tolylenediamine, 
01 by the direct combination of nitroso- 
dimethylaniUne hydrochloride and free nt- 
tolylenediamine. It is best prepared by the 
latter method. On mixing lukewarm aqueous 
solutions of the two ingredients in the proportion 
of equal molecules the blue is formed at once, 
and on cooling settles out in the shape of glisten- 
ing bronze-coloured crystals which have the 
composition CijHuN^'HCl. On adding hydro- 
chloric acid to an aqueous solution of this com- 
pound a much more soluble diacid salt 

Ci5Hi,N.-2Ha, 
of a reddish-brown colour, is formed. By the 
action of reducing agents, especially -stannous 
chloride, the leuco derivative of tolylene-blue, 
dimethyltriaminotolylphenylamine CjbHsoNj is 
formed. An aqueous solution of the blue is 
decomposed by prolonged ebullition. The pro- 
ducts of this decomposition are leucotolylene- 
blue and dimethyldiaminotoluphenazine (Tolyl- 
ene red, v. Azines). 

Literature.— Oito N. Witt (Ber. 12, 931; 
Chem. Soo. Trans. 1879, 356 ; D. E. P. 15272, 
1880 ; J. Soc. Chem. Ind. 1882, 256). R. Nietzki 
(Ber. 16, 1883, 475). 

II. Insofhehois. 
The simplest indophenol CijHjjNjO 



I 
0»H. 



NHi, 
was prepared in 1880 and described by the 
inventors, Horace Kochlin and Otto N. Witt in 
their fundamental patents: D. E. P. 15916, 
Amer. Pat. 261518, Fr. Pat. 141843, Eng. 
Pat. 1373, 5249, 1881. It may be obtained 
by any of the processes indicated for the 
purpose by theory (see above, modes of forma- 
tion). The best method for its preparation is 
the joint oxidation of ji-phenylenediamine and 
phenol dissolved in water in equimolecular pro- 
portions with oxidising agents, which act in a 
neutral or alkaline solution, such as sodium 
ferricyanide, potassium persulphate, or hypo- 
chlorites. The last-named are exclusively used 
in industrial work. The dyestufi, which is of a 



INDAMINES AND INDOPHENOLS. 



99 



reddish-blue shade, settles out at once. It is, 
hoveTer, very impure and contains other colour- 
ing matters which are formed by the condensa- 
tion of part of the indophenol formed into more 
complicated indophenols of a higher molecular 
weight. According to the D. R. PP. 179294 
and 179296, this is not the case if lead or man- 
ganese peroxides be used as an oxidising agent. 
Another method, indicated in the D. R. PP. 
160710 and 168229 consists in oxidising a 
mixture of phenol with the monoacetyl or the 
monoaryl sulphonio derivatives of j)-phenylene- 
diamine and subsequent decomposition with 
alkali. 

This dyestufi is insoluble in water, easily 
soluble in alcohol, ether, or benzene. Acids 
dissolve it readily with a yellow colour. The 
solution is quickly decomposed on standing. 

A very similar dyestufl of a bluer shade may 
be obtained by the joint oxidation of a mixture 
of j]-phehylenediamine and ji-xylenol in 
'molecular proportions. 

• Other nearly allied indophenols are prepared 
by the joint oxidation of o-toluidlne and 
p-aminophenol (CasseUa and Co., D. R. P. 
199963, 1901); and by the action of nitroso- 
phenol upon })-chloro-o-nitrodiphenylamine 
(Kalle & Co., D. R. P. 205391, 1907). 

All these indophenols are extremely similar 
in theii properties. Notwithstanding the in- 
tensity and beauty of their blue colouration 
they have not acquired any importance as 
practical dyestufis, probably because they are 
so easily attacked and decomposed by mineral 
acids. But in later years they have assumed 
great importance as raw materiiils for the manu- 
facture of very fast blue sulphur dyes and this 
has caused the appearance of numerous patents 
for the production of such indophenms, the 
more important of which only can be mentioned 
in this article. 

Dimethyl derivative of simplest indophenol, 
OuHuNjO, Q 

II 

II 

N 
I 
C.H. 

N(CH,), 
is obtained like the preceding compounds by 
joint oxidation from a mixture of phenol and 
dimethyl-jj-phenylenediamine or by oxidising 
a mixture of dimethylaniline and ^-amino- 
phenol ; it crystallises from alcohol in glistening 
green needles. Its alcoholic solution is of a 
brilliant greenish blue colour. . 

LiteriUure. — Horace Kiichlin and Otto N. 
Witt, D. R. P. 15915, 1881. Leop. Cassella & 
Co., second addition to D. R. P. 15915. 

Dimethyl-tricWorolndophenol CiiHiiCljNaO, 
N(CH3), 
i 
CjH, 



N 



is obtained by mixing alcoholic solutions of 
trichloroquinonechloroimide (1 mol.) and di- 
methylaniline (2 mol.), according to the equa- 
tion: 
C,H01a(NCl)0-f20eH5-N(CH3), 

=0ijH,iCl3Na0+CsH5N{CH3),HCl. 
RecrystaUised from alcohol, it forms long green 
glistening needles, which have the general cha- 
racter of the indophenols and are comparatively 
stable. On reduction it yields the corresponding 
leuoo compound, dimethylaminohydroxytri-' 
chlorodiphenylamine, CnHisCljNjO. 

Literature. — Schmitt and Andresen (J. pr. 
Chem. [U.] 24, 435). 

Carbazole indophenol. This curious sub- 
stance, which has' been obtained by Cassella & 
Co. according to mode of formation No. 8 from 
carbazole and nitrosophenol has evidently the 
constitution : 




jHClj 



CjHj 



It is of great importance because on being 
heated with polysulpMdes it yields hydtfon Uue, 
a sulphur dye insoluble in sodiutti sulphide solu- 
tion, but capable of being used in the vat in 
exactly the same way as indigo and giving deep 
blue shades which are quite as fine and fast as 
those obtained with indigo itself. It is therefore 
expected to become a serious competitor of 
indigo blue. {See Indigo, Abtipicial, and In- 

DIQOID DYESTUFFS ; VaT DYES, MODBBN.) 

All the indophenols mentioned so far have 
this in commoA, that they are derivatives of 
^■quinone, and this accounts for the simi- 
larity of their properties and chemical behaviour. 

A marked difference in thisrespect is shown 
by the indophenols which are derived from 
naphthaquinone which is itself less- reactive and 
consequently more stable than the benzene 
derivative. This stability also shows itself in 
the naphthindophenols which can therefore 
claim to be applicable and even valuable dye- 
stuffs. 

Although a large number of these substances 
is foreseen by theory, the only well-known 
member of the group is the one first discovered, 
the typical indophenol of commerce CigHuNjO 
(vat blue, Kiipenblau), the structure of w^ch is 
expressed by the constitutional formula 





100 



INDAMINES AND INDOPHENOLS. 



It was discovered in 1880 by Horace Kophlin 
and Otto N. Witt and described in their funda- 
mental indophenol patents already mentioned. 

It is prepared from an alkaline mixture of 
dimethyl-j)-pheuylenediamine and a-naphthol 
in molecidar proportions by oxidation. On a 
small scale potassium ferricyanide or ammonium 
persulphate is the most convenient oxidising 
agent, whilst on the manufacturing scale air is 
blown through the liquid, or a solution of sodium 
hypochlorite is employed. It may also be pre- 
pared by adding potassium chromate to the 
alkaline mixture of the ingredients and acidify- 
ing with acetic acid. Another process consists 
in simply heating on the water-bath an alcoholic 
solution of free uitrosodirnethylaniline and 
sodium o-naphthoxide ; or in bringing together, 
in an aqueous solution, a-naphthol, nitrosodi- 
methylaniline, and caxistic soda ; this mixture is 
rapidly transformed into indophenol if a small 
quantity of a reduping agent, such as sodium 
stannite or glucose, be added. 

Indophenol forms a dark-blue miorocrystal- 
line powder with a coppery metallic lustre, 
exactly resembling indigo. It is quite insoluble 
in water, sparingly soluble in spirit, ether, .or 
benzene. It dissolves in dilute mineral acids, 
forming salts of a yellow colour, which are, 
howev;er, quickly decomposed. In this decom- 
position a-naphthaquinone is formed as one of 
the products. Indophenol is slightly volatile ; 
on being strongly heated it forms a sublimate 
resembling sublimed indigo. By reducing agents 
it is transformed into its leuoo derivative 

CisHisN^O, 
dimethyla minophenylhy droxynaphthylamine. 
This has been an article of commerce under the 
name of indophenol-white. It is quite stable in 
an acid state, but in the presence of alkalis it 
rapidly absorbs the oxygen of the~air, indophenol 
being regenerated. 

The application of indophenol to dyeing and 
calico-printing is based either on the formation 
of the dyestuS on the fibre, or on the oxidation 
of its ready-formed leuco derivative after fixing 
the latter on the fibre. The first method is 
rarely employed. As an example the follow- 
ing description, taken from the patent specifica- 
tion, may serve. Bleached calico is printed with 
a thickened mixture of aminodimethylaniline and 
Bodiiim a-naphthoxide ; after drying and steaming 
it is passed through a solution of potassium di- 
chromate, when the blue is instantaneously de- 
veloped. As a rule ready -formed indophenol is 
employed for printing, reduced by being mixed 
witn a solution of stannous acetate, then 
thickened, with starch paste and printed on the 
fibre. The colour is developed by steaming 
and exposure to the air. Indophenol-blue on 
calico is very fast to the action of soap, fairly so 
to the action of light, but rather susceptible to 
acids. * 

In spite of its many good qualities, indo- 
phenol at first did not meet with an enthusiastic 
reception in the tinctorial world. This was 
changed by an interesting and for its time (about 
1885-1895) important discovery of the Swiss 
manufacturing firm L. Durand, Euguenin & Co. 
It is based on the fact th^t indophenol, mixed 
with indigo, assumes the properties of the latter 
and may consequently be used in the vat pro- 



cess, especially with hydrosulphite as a reducing 
agent. 

It is more than probable that the two leuco 
compounds of indigo and indophenol are capable 
of combining chemically and that the resulting 
substance is endowed with strong affinities for 
the fibre, especially cotton. It is thus easily 
taken up from the vat and, on being reoxidised 
on the fibre, deposits in the molecular interstices 
of the lattei an intimate mixture or even a 
chemical combination of the two ^yestuffs, 
indigo and indophenol. 

. An intimate mixture of indigo and indo- 
phenol, ground together into an impalpable 
powder is the ' vat blue ' or ' kiipenblau ' of 
commerce, which may still occasionally be met 
with, although it has lost many of its advantages 
by the great reduction in the price of indigo and 
by the introduction of the cheap and excellent 
dark-blue sulphur dyes, man^ of which are also 
capable of being applied in the vat. 

Literature. — Otto N. Witt and Horace* 
Kochlin, D. R. P. 15915, 1881, with several, 
additions; and corresponding patents in Eng- 
land, France, the United States, Sweden, Bel- 
gium, and Austria ; Otto N. Witt, J. Soc. Chem. 
Ind. 1882, 144, 225, 405 ; E. Mohlau, Ber. 16, 
2845. 

III. Acid Indophenols. 

It has already been mentioned that these sub- 
stances are not true acids, containing no carboxyl 
groups in their molecule. They owe their name 
to the fact that, containing no amino and 
several hydroxyl groups, they readily combine 
and form stable salts with metallic oxides. Of 
these only the alkali salts are known. In a solid 
state they form crystalline powders with a green 
or copper-coloured metallic lustre. They are 
easily soluble in water with an intense blue 
colouration. By the addition of acids the free 
indophenols are deposited in the shape of brown 
or reddish flakes, which are soluble with a dark 
red colour in spirit, ether, benzene, and analogous 
solvents. 

The acid indophenols show in even a higher 
degree the tendency of the whole group to 
polymerise into colouring matters of a more 
complex molecule. It is therefore extremely 
difficult to prepare them in a state of purity, v 
On the other hand, they do not show the 
susceptibility to acids so characteristic of the 
indamiues and typical indophenols. It is there- 
fore possible to prepare them not only in alkaline 
but also in acid solutions and by means of 
oxidising agents which act in such. Their 
modes of formation are given above under 
methods 4, 6, 7, 12, and 15. 

Typical acid indophenol Ci^HgNO,, 
O 

C,H, 



I 



C,H4-0H 
The possibility of preparing this compound by 
the joint oxidation of ^-aminophenol and 
phenol is mentioned in Kochlin and Witt's 
fundamental indophenol patents, but its manu- 
facture seemed at first to ofEer no interest. It 



INDANTHRENE. 



101 



is formed if C[uinoneimideia brought into contact 
with phenol, and B. Hiraoh observed it on 
adding caustic potash to a solution of quinone- 
chloroimide in phenol, but did not succeed in 
isolating it (Ber. 13, 1909). The cause of these 
difficulties was revealed by the D. R. P. 15V288 
of the ActiengeseUschaft filr Anilinf abrikation of 
Berlin. The formation of the dyestufE must take 
place at unusually low temperatures if its 
tendency for polymerisation in a nascent state 
is to be overcome. According to this patent, 
the product may be prepared with a good yield 
if an equimolecular mixture of phenol and 
p-aminophenol be oxidised with sodium hypo- 
chlorite at a temperature of — 15° to — 18°, prefer- 
ably in solutions saturated with sodium chloride 
80 that the sodium salt of the dyestufE is at once 
salted out of the liquid. It is thus obtained in 
the shape of glistening metallic green needles. 

These dyestufEs become more stable and are 
therefore more easily prepared if their molecule 
be weighted by the introduction of various 
substituents : 

Acid dibiomoindophenol Ci^H^BrgNO,, 
O O 



C,H,Br, or 



u 



N N 

C„HjOH C, 

(See remarks on migration under 2 and 6.) 
has been prepared in various ways by R. Mohlau 
(Ber. 16, 2843). It may either be obtained by 
the joint oxidation of a mixture of dibromo- 
aminophenol and phenol in molecular propor- 
tions, or by adding dibromo-quinonechloroimide, 
suspended in alcohol, to an alkaline solution of 
phenol. The sodium salt of the indophenol 
separates out in green glistening needles, which 
are soluble in water and alcohol with a pure 
blue colour. On adding acetic acid to the solu- 
tion the free indophenol settles out in dark-red, 
almost black prisms with a metallic lustre. It 
is soluble in alcohol with a magenta colour. 
Mineral acids decompose this compound into 
dibromo-aminophenol and y-quinone. If a 
current of sulphur dioxide be introduced into 
the solution of the sodium indophenolate, the 
corresponding leuco compound CijHjBrjNOj, 
dihydroxydibromodiphenylamine, is formed. It 
crystallises in white glistening needles, melting 
at 170°. 

Acid dimethylindophenol CnHiaNOj, 
O 






CH, 



/ 



\ 



\/ 



!CH, 



N 

I ' I 

CeHs,(CH3)jOH CaH^OH 

is also much more stable and therefore more 
easily prepared than the typical acid indophenol. 
This was shown in 1902 by L. Casaella & Co. in 
their D. R. P. 191863 and the corresponding 
Eng. Pat. 4653, 1902 ; 2617, 1902. According 
to these patents, 1:4: 6-(j)-) xylenol and p- 
aminophenol give a good yield of this dyestufE it 



subjected to joint oxydation in equimolecular 
proportions. 

All these acid indophenols have assumed a 
new interest and are being largely investigated, 
since it has been shown that they are valuable 
raw materials for the manufacture of the sulphur 
dyes which have come so much to the front in 
these later years. O. N. W. 

INDANE V. Indenb. 

INDANTHRENE. Within recent years, con- 
siderable advances have been made in the dis- 
covery and commercial production of certain 
compounds belonging to the class of the vat 
dyes. By the term ' vat dye ' is understood an 
insoluble pigment which, when reduced by an 
alkaline reducing agent, passes into a hydro 
derivative soluble in the alkaline reducing 
solution. The hydro derivative is absorbed by 
fabrics steeped in this solution and is then re- 
converted into the pigment when the material 
ia exposed to the oxidising action of the air. 
Indigo, the most important of all colouring 
matters, is a typical vat dye, and it is am>arent 
that the process entailed by the use oi these 
colours not only produces the shades fastest to 
light and washing but is also one of the simplest 
with which the dyei has to deal. 

For many years research on the formation 
of new vat dyes was confined to the indigo 
group, but in the year 1901 it was demonstrated 
by R. Bohn that certain derivatives of anthra- 
quinone could be applied for this purpose. The 
vat dyes of this series possess, however, one 
important property which distinguishes them 
from all other members of the class, that is, the 
vat formed by the alkaline reduction of the 

gigment is always strongly coloured. The 
ydro derivatives are, therefore, themselvea 
coloured substances, whereas the hydro deriva- 
tives from other vat dyes, for example indigo 
white, are colourless or at most faintly yellow. 

The vat dyes of the indanthrene series may 
be conveniently divided into five groups ; — 

(1) Indanthrene. 

(2) Flavanthrene. 

(3) Benzanthrone colours. 

(4) Anthraquinoneimide colours. 

(5) Acyl derivatives of aminoanthraquinoue. 
Indanthrene : Preparation (R. Bohn, 

D. R. P. 129845; Zusatze, 129846, 129847, 
129848, 135407, 135408, 138167, 155415, 210223, 
and 216891 ; Soholl and Berblinger, Ber. 1903, 
36, 3427). 

The colouring matter is prepared by fusing 
;3-aminoanthraquinone with caustic potash at 
200°-300° and is found in the melt as the soluble 
potassium salt of the blue hydro derivative of 
indanthrene which, when dissolved in water with 
free access of air, is converted into the insoluble 
blue colouring matter. At a lower temperature 
(150°-200°) alizarin is formed at the same time 
as indanthrene, but at the higher temperature 
this is transformed into a brown substance 
soluble in alkali ; the separation of the blue 
colouring matter is, therefore, simple owing to 
its insolubility in the alkaline liquid. Whether 
produced at the higher or lower temperature, the 
indanthrene is not a homogeneous substance but 
consists of two compounds, indanthrene a and 
indanthrene b, the latter being worthless as a 
colouring matter. It is possible so to regulate 
the concUtions as to cause indanthrene A to be 



102 



INDANTHEENE. 



the chief product ; thus, when the fusion is 
canied out in the piesence of potassium nitrate 
the product consists almost entirely of indan- 
threne a, and indanthrene b is only formed in 
small amount. By fusing iS-aminoanthra- 
quinone with caustic potash at a still higher 
temperature, that is at 330°-360°, the product 
is a yellow vat dye, flavanthrene {v. infra). 

600 grams of caustic potash together with a 
little water are placed in a nickel basin which 
is heated by means of an anthracene bath. The 
melt is then heated to 200° and mixed with 
20 grams of potassium nitrate; 100 grams of 
/3-aminoanthraquinone are now gradually added 
with constant stirring. The temperature is 
raised tb 260° and maintained at this point 
for half an hour when the melt is poured into 
water, the solution boiled, and the precipitated 
colour filtered and washed. The small quantity 
of indanthrene B present in the product is 
separated by taking advantage of the greater 
solubiUty of its hydro derivative in dilute alkali. 
100 grams of the crude indanthrene in the form 
of paste are diluted with 10 litres of water and 
warmed to 60°-70°; 200 grams of a 26 p.c. 
caustic soda solution and 1500 grams of sodium 
hydrosulphite solution (sp.gr. 1-074) are then 
added and the temperature of the mixture 
maintained at 60°-70'' for 1 hour. By this 
time the colour will have completely dissolved, 
and. the solution, when cooled, will dowly 
deposit the sodium salt of the hydro derivative 
of indanthrene a as well-defined glistening 
needles with marked coppes reflex. The salt is 
collected by filtration, washed with a little 
dilute caustic soda solution to which a small 
quantity of _ hydrosulphite solution has been 
added, and is then converted into pure indan- 
threne A by dissolving in hot water and allowing 
free access of air. The brown-red mother liquor 
contains the more soluble salt of the hydro 
derivative of indanthrene b from which the 
colour separates as blueish-green floclcs when air 
is led into the solution. 

Indanthrene prepared in this manner is a 
dark blue powder vrith strong metallic reflex, 
and^is practically insoluble in all the usual 
solvents. It dissolves with great difficulty in 
boiling aniline and in nitrobenzene, in the latter 
case to the extent of one part in 6000, forming 
a greenish blue solution. It dissolves to the 
extent of 1 part in 600 in boiling quinoline, 
forming a blue solution from which the colour 
separates as characteristic curved needles re- 
sembling pure indigo in appearance ; the solu- 
tions are without fluorescence. When heated 
it partly sublimes in the form of its charac- 
teristic needles and then decomposes with char- 
ring between 470° and 600°. 

Gonstilution of indanthrene (Soholl, Ber. 
1903, 36, 3410). Indanthrene as shown by its 
elementary analysis and molecular weight 
determination by the ebullioscopic method in 
quinoline has the molecular formula CajHuOiN. 
and is therefore formed by the condensation of 
two molecules of /3-aminoanthraquinone with 
loss of 4 atoms of hydrogen. 

2C,4H80,N-4H -» C,aHi.O,Ng. 

That these 4 hydrogen atoms are not re- 
moved from the amino groups alone — ^in other 
words, that an azo compound is not formed — is 



shown by the fact that indanthrene when re- 
duced does not yield jB-aminoanthraquinone or 
a reduction product of this base. Moreover, as 
indanthrene no longer contains a free amino 
group, it is probable that two of these hydrogen 
atoms are supplied by the two amino groups 
and that the other two belong to the rings 
bearing the amino groups in the two molecules 
of j3-aminoanthraquinone taking part in the 
reaction. From the fact that 1 : 2-dihydro^an- 
thraquinone (alizarin) is always a product of the 
fusion in its earher stages, it is reasonable to 
assume that the hydrogen atoms removed from 
the two rings are those in the ortho position to 
the two amino groups. This leads to two 
formulae for indanthrene, namely — 

CO 




fS-AminoanthTaquinone residuo. 



CO 



CO 



NH 



CO 
(1) 



CO 

CO 
CO 

12) 



NHl 



Since indanthrene is not reduced to a 
diamine, which would be the case if it possessed 
an ortho diazine formula represented by (1), it 
follows that it must be a dihydro paradiazine 
represented by formula (2), or in other words, 
that it is ^-dihydro-1 : 2 : 2' ; I'-anthraquinone- 
azine. This view of the structure of indanthrene 
is completely upheld by its chemical behaviour. 
It has been suggested by Nietzki (Chemie der 
Organ. Farbstofie, 6 Aufl. S. 121, 1906) that the 
formation of indanthrene is due to the inter- 
mediate production of l-hydroxy-2-aminoanthra- 
hydroquinone, two molecules of which combine 
to form tetrahydroindanthrene. This has, 
however, been disproved by Scholl, Berblinger, 
and Mansfield (Ber. 1907, 40, 320), who find that , 
neither l-hydroxy-2-aminoanthrahydroquinone 
nor l-hydroxy-2-aminoanthraquinone yields in- 
danthrene when fused with potash. 

Properties of indanthrene. — ^When indan- 
threne in dilute alkaline solution is heated at 
40°-60° with sodium hydrosulphite, it passes 
into a blue hydro derivative, dihydroindan- 
threne. This substance possesses the property 
of dyeing unmordanted cotton blue, and when 
the fibre so dyed is exposed to the oxidising 
action of the air the hydro derivative is 
reconverted into indanthrene. When indan- 
threne is reduced by zinc dust, a brown hydro 
derivative is formed ; this hydro derivative is 
also converted into indanthrene on exposure to 
the air. Soholl, Steinkopf, and Kabacznik (Ber. 
190*7, 40, 390) have shown that the blue sub- 
stance is ^-dihydro-l:2:2': I'-anthraquinone- 
anthrahydroquinoneazine(l), and that the brown 
solution contains ^-dihydro-1 : 2 : 2' ; I'-anthra- 
hydroquinoneazine (2). 



INDANTHRENE. 



103 



CO 



(XXX 



CO 
NHI 



\ 







yaro 




(1) 
Blue hydro derivative. Brown hydro derivative 

The oomponnd oommercially 'known as. 
indanthrene S is the disodium salt o£ formula 2, 
and this is the substance which is always formed 
in the indanthrene vat. 

When indanthrene is oxidised by nitric acid 
(sp.gr. 1-24), it is converted into the yellow 
1:2:2': I'-anthraquinoneazine (Scholl and Ber- 
blinger. Ber. 1903, 36, 3427; cp. SohoU, Ber- 
blinger, and Mansfield, ibid. 1907, 40, 321). 
CO 



CO 

CO 

This substance is reconverted into indan- 
threne on reduction, a reaction which may be 
efiected by means of direct sunlight. 

Indanthrene is one of the most stable sub- 
stances known; sodium hypochlorite, which 
destroys most colouring matters such as the 
alizarins, indigos, &c., merely converts indan- 
threne into the above yellow azine, which can be 
readily reconverted into indanthrene by means 
of sodium hydrosulphite. 

When halogen atoms enter the molecule of 
indanthrene, the shade becogies greener. In- 
danthrene blue GC (B. E. P. 138167) is a brom- 
indanthrene ; indanthrene blue GCD and CE 
are chloro derivatives (D. B. P. 16S416). Mono- 
chlorindanthrene is prepared by the action of 
boiling concentrated Jiydrocluoric acid on 
anthraquinoneazine whereby chlorination and 
reduction take place simultaneously — 

N IPht NH jPht 

XXXX /v / 

Phtf N Pht| NH 

Pht=Phthaloyl 0,Hi<^q 

The reaction is analogous to the formation 
of chlorhydroquinone from quinone and hydro- 
chloric acid. Owing to the alkaU required in 
the preparation of the indanthrene vat, this 
substance cannot be used for the dyeing of wool. 
The sulphonio acid (D. R. P. 216891) can be 
employed, however, for this purpose. The blue 
produced on cotton by the aid of indanthrene is 
one of the fastest known. (For the method of 
dyeing compare D. R. P. 139834 ; for printing, 
compare D. R. P. 132402, 140573.) 

Flavanthrene (indanthrene yellow). As 
already mentioned, flavanthrene was discovered 
by R. Bohn (D. R. P. 138119), in the products 



formed by the fusion of ;3-aminoanthraquinone 
with potash. At the present time it is prepared 
by treating ;3-aminoanthraquinone with anti- 
mony pentachloride in boiling nitrobenzene. ( F. 
art. Flavanthebnb.) 

When reduced by alkaline hydrosulphite, 
flavanthrene yields a violet-blue vat in which 
cotton is dyed a deep blue ; when exposed to 
the oxidising action of the air the colour changes, 
in the course of a few minutes, to the light yellow 
of flavanthrene. 

Preparation. — ^Ten grams of ;3-aminoanthra- 
quinone are gradually added to a solution of 
35 grams anhydrous antimony pentachloride in 
100 grams nitrobenzene, heated at 60°-80°. 
The mixture is then heated to the boiling-point 
ajid maintained at this temperature for one hour, 
the containing flask being without a condenser. 
The yellow-brown solution deposits, on cooling, 
chemically pure flavanthrene as brownish-yellow 
needles. , 

The eonstitiition of flavanthrene has been 
determined by Scholl (Ber. 1907, 40, 1691). 
The molecular formula is OjsHjjOjNj, and it 
must therefore be formed from ;8-aminoanthra- 
quinone in accordance with the equation 

20,jH,0,N -> Ca8H„0,N,-|-2H-f-2HjO. 

The two molecules of water formed in the 
reaction at once suggest the interaction of the 
hydrogen atoms of the amino groups with the 
carbonyl oxygens, an assumption which leads to 
the following formula : — 

bo 

/v 






CO 



NH, 



r 



CO 



N. 






+m^o 



CO 



The ring then closes thus : 
CO 




-J-2H. 

The hydrogen thus formed is not eliminated 
in the free condition, but reduces the colour to 
the dihydro base, the state in which it always 
occurs in the melt. 

This view of the constitution of flavanthrene 
has been confirmed by Scholl by the actual 
synthesis of this substance in the following way : 
2-methyl-l-aminoanthraquinone (1) is con- 
verted into 2 : 2'-dimethyl-l : I'-dianthraquinonyl 
(2) either by heating the corresponding iodide 
with copper powder or by the action of copper 
powder and acetic anhydride on the diazonium 
sulphate : 



104 



INDANTHRENE. 



CO 



y^"' 



CO I 

I CO 



(1) (2) 

This substance is then oxidised to the di- 
carboxylic acid which is converted, through the 
acid cliloride, into the acid amide (3). An 
attempt to prepare the amino compound from 
this by the action of bromine and potash led to 
the formation of flavanthrene : 



CO 



/\ 



ICONHj 




I CO 
NHj-CO/V'Y^. 

CO 
(3) 
Pyranthrene (indanthrene golden orange) 
(D. R. P. 175067 ; Bor. 1910, 43, 346 ; R. 
SchoU). This substance is a valuable orange 
vat dye which is formed by the elimination of 
two molecules of water from 2 : 2'-dimethyl-l : 1'- 
dianthraquinonyl (formula (2) above). It differs 
from flavanthrene in having two methin groups 
in place of the azine nitrogen atoms : 
CO CO 




000 




CO 

The condensation proceeds readily in the 
presence of a dehydrating agent such as zinc 
chloride or by merely heating alone at 350°-380°. 
Pyranthrene forms a magenta red vat with 
alkaline hydrosulphite in which cotton is dyed 
a deep red ; on exposure to the air this oxidises 
to a fast orange. 

The entrance of halogen atoms into the mole- 
cule of pyranthrene reddens the shade and of 
these derivatives dibromopyranthrene (D. R. P. 
218162) is the most red. 

The benzanthrone colours. The vat colours 
of this class were discovered by O. Bally (Ber. 
1905, 38, 194 ; D. R. P. 176018), who found that 
when the Skraup quinobne synthesis was appUed 
to 2-aminoantbraquinone, two glycerol residues 
entered into the moleotde, fotming benzanthron- 
quinoline (1) 



A 




A 




a) 



\/ 



(2) 



When this reaction was applied to anthia- 
quinone, benzanthrone (2) was formed. 

Blue vat dyes are formed from these sub- 
stances on fusion with potash, two molecules 
condensing with loss of four atoms of hydrogen. 
To this group belong indanthrene dark blue 
(D. R. P. 185221) as well as its isomeride and 
halogen substitution product, indanthrene violet 
(D. R. PP. 177574, 194252, 217670); indan- 
threne green (D. R. P. 185222) is an amino- 
derivative of indanthrene dark blue ; if the last- 
named colour is stron^y chlorinated a deep, 
very fast black is formed. Cyananthrene and 
vlolanthrene also belong to this group. 

Colours derived from anthraquinoneindde. 
These colours consist of several anthraquinone 
residues joined togethei in much the same 
manner as in flavanthrene. They are, for the 
most part, trianthraquinonediimides and their 
Substitution products which are formed by the 
condensation of aminoanthraquinoties and halo- 
genanthraquinones. Indanthrene Bordeaux 
(D. R. PP. 184905 and 206717) and indanthrene 
red (D. R. P. 197554) belong to this group. 

Acyl derivatives of amlnoanthraquinone. 
Colours of this group are derived from autiira- 
quinonepyridone : 

CO 




by the replacement of the hydrogen atom in the 
para- position to the imino group by arylamino 
residues. Thus algol red is formed when 
1-bromanthraquinone (1) is converted into 
methyl-1-aminoanthraquinone (2) by means of 
methylamine. This is acetylated and con- 
densed to itT-methylanthraquinonepyridone (3), 
which is then brominated, yielding 4-brom-iV- 
methylanthraquinonepyridone (4), and this, on 
condensation with 2-aminoanthraquinone, yields 
algol red (5) : 



CO Br 

000 



CO NHCH, 



CO 
(1) 




jN-CH, 



CHjj^.N-CHa CH/ \N-CH, 



ooo-ooo 



CO Br 



C4) 



CO 



"<y^ 



C6) 



INDENE 



106 



Other members of this class are algol yellow, 
algol rose, algol scarlet, algol green, algol blue,' 
and algol brown. They all yield coloured vats 
with sodium hydrosulphite in which cotton is 
dyed the colour of the dihydro derivative ; on 
exposure to the air the colour on the fibre is 
quickly oxidised to the algol dye. 

The following indanthrene colours are formed 
from anthraquinone derivatives by the aid of 
various reactions, 'but have not as yet had a 
definite constitution assigned to them. Indan- 
threne maroon (D. R. P. 160814) and indanthrene 
grey (D. R. P. 157685) are derived from diamino- 
anthraquinones. Indanthrene orange and in- 
danthrene copper (D. B. P. 198048) are prepared 
from the acetyl derivatives of aminoanthra- 
quinone by means of phosphorus oxychloride. 
Cibanon yellow, cibanon orange, and cibanon 
brown, are derived from methylanthraquinone 
and its derivatives. J. P. T. 

INDAZINE V. AziKES. 

IKDENE. The compounds of the indene 
group are derived from the hydrocarbons 
mdene and hydrindene 



CH 

CO 

CHj 
Indene. 



CHj 

Hydrindene. 



by the replacement of the hydrogen atoms 
either in the five-membered ring oi in the 
aromatic nucleus. They therefore yield two 
classes of derivatives: (1) Those of aromatic 
character which are formed when the hydrogen 
atoms of the benzene ring are substituted. 
(2) Those of aliphatic character which are pro- 
duced by the replacement of the hydrogen 
atoms attached to the five-membered ring. 

Constitution. — ^The constitution of indene 
follows from its conversion into homophthalic 
acid by oxidation with permanganate : 



40 /V-CHjCOOH 
CH ^ IJ— COOH 

CHj 



and the structure of hydrindene is shown by the 
production of this substance from indene by 
reduction with sodium and alcohol. 

Oceuirenee and preparation of indene and 
indene derivatives. Indene was isolated from 
coal-tar by Kramer and Spilker (Ber. 1890, 23, 
3276) who obtained it from the higher boiling 
fraction of the h'ght oil in which it occurs to the 
extent of about 30 p.c. It is formed, accom- 
panied by hydrindene, in the dry distillation of 
paraindene (0,Hj)a;, a white substance which is 
formed when benzene containing indene is 
treated with concentrated sulphuric acid (Ber. 
1900, 33, 2261). It has, moreover, been pre- 
pared synthetically by Perkin and Revay 
(Chem. Soc. Trans. 1894, 65, 228 ; cp. Kipping 
and Hall, ibid. 1900, 77, 469), by the distillation 
of barium hydrindenecarboxylate, a substance 
which can be prepared from o-xylylene dibromide 
by the following series of reactions. 



<^«H«<CH'Br+NaiiC(CO(>R). 



~> OeH.<^|^>C(COOH), 

~> CeH,<^^i'^H-COOH 

Hydrlndene-2-carboxylio acid. 
CH 

-> C.H,<^VH-f Hj+COj. 

Owing to the ease with which the five- 
membered ring is usually formed, derivatives of 
indene and of hydrindene are readily produced 
from the corresponding benzene derivatives, 
having a, side chain containing the requisite 
number of carbon atoms. The benzene deriva- 
tives which lend themselves to tlus change may 
therefore be divided into two classes : (1) those 
having one side chain of three carbon atoms; 
(2) those having two side chains, attached in 
the ortho position to the benzene nucleus, 
one of these side chains being composed of 
one carbon atom the other of two carbon 
atoms. 

The derivatives of hydrocinnamic acid fall 
within the first class and a large number of 
indene compounds have been prepared from this 
substance and its derivatives {v. Miller and 
Eohde, Ber. 1902, 35, 1762), 

The general character of this reaction may 
be expressed by the scheme 




(X=halogen). 

As an illustration of the f(Smation of hydrin- 
dene derivatives by the method indicated under 
class (2), the formation of 1 : 3-diketohydrindene 
can be given. The ethyl salt of the carboxylio 
acid of this substance is formed when ethyl 
phthalate is condensed with ethyl acetate in the 
presence of sodium or sodium ethozide (W. 
Wislicenus, Ber. 1887, 20, 693). 



-COOCA , m 
DOOCX + ™» 

CO 



■COOCaH, 



/CHCOOCjHj -f 2CsH.0H. 

;\^o 

A curious molecular rearrangement, leading 
to the formation of hydrindene derivatives, has 
been discovered by Gabriel and Neumann (Ber. 
1893, 26, 951). The condensation of phthalio 
anhydride and sodium acetate in the presence 
of acetic anhydride leads to the formation of 
phthalylacetic acid : 



'CO- 



CeH4<^^Q^0 + CH,-C00H 



->C„H 



C:CH-C00H 






and this substance, when treated with sodium 
methoxide, passes into a derivative of 1 : 3-diketo- 
hydrindene. The reaction may be explained as 
follows ; — 



106 



INDENE. 



CO 



C : CHOOOH 

-^PTT^C(OH):CHCOOH 

-^ ^6^*<^C00Na 

It can be applied to the preparation of numerous 
derivatives of 1 : 3-diketohydrindene. 

The formation of indene derivatives from 
compounds containing the naphthalene nucleus 
in which the stability of the rjng is weakened by 
the presence of strongly negative groups has 
been investigated by Zincke and his pupils (Ber. 
1886,19,2500; 1887,20, 1265,2894,3216; 1888, 
21, 491, 2381, 2379 ; 1894, 27, 744 ; Annalen, 
1892, 267, 319; 1894, 283, 341; 1898, 300, 
197). This type of reaction may be illustrated 
by the transformation of diohloro-/3-naphtha- 
quinone into dichlorohydroxyindene carboxylio 
acid by the action of caustic alkali. 
OH OH 

y. Nc^COOH 

\/\cca:CHa 

Hypothetical 
intennediate product. 

C(OH)COOH 

ca 

Derivatives oi hydrindene can also be formed 
from ortho benzenoid dinitriles. Thus o-pheny- 
lenediacotonitrile'passes into j8-imino-o-cyano- 
hydrindene when its solution in alcohol, contain- 
ing a trace of sodium ethoxide,i8 warmed (Moore 
and Thorpe, Chem. Soo. Trans. 1908, 93, 165). 

aCH,-CN ^ 

-» ] T "C:NH 
CHj-ON 

Preparation of indene from coal-tsr. The 
fraction boiling at 176°-182° obtained from 
crude benzene is first titrated with bromine and 
the amount of unsaturated material present 
determined. A sufficient quantity of picric acid 
is then added to the hot liquid and the crystal- 
line material which separates is isolated by 
filtration. The impure picrate is then distilled 
with steam, under which conditions the naphtha- 
lene picrate contained in it is only slowly decom- 
posed whereas the indene picrate is readily trans- 
formed into indene which passes over with the 
steam. The crude hydrocarbon is then again con- 
verted into the picrate and the operation repeated 
until pure indene is obtained. Indene picrate 
forms golden yellow needles which melt at 98°. 

Indene is a clear mobile liquid boiling at 
179-5°-180-5° (oorr.). 

It is obtained pure only with great difficulty, 
as it rapidly absorbs oxygen from the air and 
when kept in a sealed vessel polymerises to a 
resin. The most convenient synthetic method 
for the preparation of indene is from o-hydrin- 
done, the oxime of which passes on reduction 
into 1-aminohydrindene, and when the hydro- 



CO'-" 

CE-CN 



chloride of this base is distilled, ammonium 
chloride and indene are formed, thus — 
CHj CHj 

C.H4/>CHs ^"^^ C.H./\CH, 

Yo "^ Y:NOH 

a-Hydrindone. Oxlme. 

CHj CHa 

^+^Cl c,H,^0Hj->C,H4/NcH+NH.Cl 

CH-NHj-HCl CH 
l-Aminohydrindene Indene. 
hydrochloride. 
Reactions of indene. Indene readily com- 
bines with bromine, forming 1 : 2-dibromohydrin- 
CHj 

dene CaH^/^NcHBi! and when oxidised passes 

OHBr 
first into hydrindene glycol and then into homo- 
phthalic acid 



^«^*<CH^°^"^ C,H.<^ -^CHOH 



•CHOH 
■^CHC 
CHj 

"^ ^»^«<X'00H 



IHaCOOH 



The hydrogen atoms of the methylene group 
present in indene are reactive ; thus, when the 
hydrocarbon is condensed with benzaldebyde, 
benzylidene indene is formed : 

<^«'^'<Ch"^C1H + OHCCeH, 

-> C,H.< -^CH 

^C:HCC,H5. 
In fact, this grouping behaves in much the 
same manner as the corresponding complex in 
ethyl malonate and analogous compounds; 
thus, when indene is treated with methyl iodide 
and powdered alkali, methyl indene is formed 
(Maickwald, Ber. 1900, 33, 1504) : 

C6H.<;^g^CH + CH,I + KOH 

CH 

~> C,H,<^CH-|-KI + nfi. 

CHCH, 

Hydrindene (Indane) C8H4<^ggp>CHj. 

This hydrocarbon can be prepared by dissolving 
1 part of indene in 10 parts of 90 p.c. alcohol and 
adding metallic sodium in small portions until 
the product is no longer converted into a resin 
by concentrated sulphuric acid. It is a mobile 
oil boiling at I76''-176-5° (corr.). 

The ketones derived from hydrindene. The 
ketones derived &om this substance may be 
classified as follows : (1) The mono-ketones 
(hydrindones), which comprise : 

a-Hydrindone. 0-Hydrindone. 

(2) The di-ketones (di-ketohydrindenes), 
which are 

c.H<ro>CH. CeH<^;>co 

1 : 8-Diketohydrindene. 1 : 2-DiIcetohydrlndene.' 
> This substance has been prepared by Perkin, 
Roberts and Eoblnaon (Chem. Soo. Trans. 1912, 101, 
232) from isonitroBO-a-hydrindone (Kipping, ibid. 1894, 
65, 492). It crystallises from benzene as golden yellow 
plates, m.p. 95°-116°, and gives a semicorbazone (m.p. 
230''-2S3° with decomposition), an osazone (m.p. 280 - 
235°), and an indenoqulnoxaline (m.p. 164°-105°). 



INDIAN INK OR CHINESE INK. 



107 



(3) The tri-ketone is 



C.H.<gO>CO 
1:2: 3-Trlketohydcindene. 

o-HydrindoneC,H4<^^«^CHa. This sub- 
stance is best prepared by the action of aluminium 
chloride on the chloride of hydrocindamlc acid 
in accordance with the following equation : — ' 
CHj CHj 

figtJH, -» fW3H, +HC1. • 

COCl CO 

It forms rhombic plates from dilute alcohol, 
melts at 40° and boils at 243°-245°. The oxime 
melts at 146° and the phenyl hydrazone at 
130°-131°. The methylene group adjacent to 
the carbonyl group in o-hydrindone is reactive 
and derivatives of the ketone can be formed by 
the usual reagents. Thus amyl nitrite gives the 
ozime of 1 : 2-diketohydrindene 

and the action of benzaldehyde leads to the 
formation of the benzylidene derivative 

C«H4<^p-g-^^^>C ; CHC.H,. 

;3-HydrindoneC,H4<^^»^CO. Thisketone 

is best prepared from ^-imino-a-cyanohydrindene 
by distilling with dilute sulphuric acid (Moore 
and Thorpe, Chem. Soc. Trans. 1908, 93 ; c/. also 
Chem. Soc. Proo. 1911, 27, 128). 

CeH.<gi'>CO 



^C 
DH-I 



NH 

■ON 



It can also be prepared from the indene of coal- 
tar (Heusler and Schiefier, Ber. 1899, 32, 28). 
The method most convenient for this purpose is 
to convert indene into the oxyohloride by the 
method of Kramer and Spilker (Ber. 1890, 23, 
3280) and then to transform this into the 
methoxy derivative which, with dilute sulphuric 
acid, yields ;8-hydrindone : 

• /CHCl /CHOCH, 

C,H,O>CH0H -^ C,H4<' >OHOH 

-> C,H.<C|«>CO. 

It can also be formed by distilling the calcium 
salt of o-phenylenediacetic acid (Benedikt, 
Annalen, 1893, 275, 353; Sohad, Ber. 1893, 
26, 222) : 

^•^•<ci:-co8>c^-^C'H'<§<^-^^''«°' 

/3-Eydrindone crystallises from dilute alcohol 
as long needles, melts at 61° and boils with 
partial decomposition at 220°-225°. The oxime 
melts at 165°, the phenylhydrazone at 120° and 
the semi-carbazone at 210°. 

1 : 3-Diketohydrindene C,Hi<^q^CHj, is 

probably the best known derivative of indene 
and is formed by the method of W. Wislicenus 
already described. It may be isolated (Kauf- 
mann, Ber. 1897, 30, 385) by dissolving the 



sodium compound of ethyl diketohydrindene- 
oarbozylate, prepared from ethyl phthalato and 
ethyl acetate, in as little boiling water as possible, 
cooling to 70°-76° and adding dilute sulphuric 
acid. A vigorous evolution of. carbon dioxide 
then ensues and the diketone separates in the 
crystalline form. I:3-diketohydrindenemeltsand 
decomposes at 129°-13I°. 

As is to be expected, the methylene group 
between the two carbonyl complexes of 1 : 3-di- 
ketohydrindend is exceedingly reactive and this 
substance shows all the reactions of the /3-dike- 
tones. When oxidised by hydrogen peroxide 
or potassium persulphate, it is converted- into 
the oxygen analogue of indigo, having the 
formula 

0,H4<^QQ^C : C<^QQ^CsH, 

This substance crystallises from aniline as 
glistening red needles. 

1 5 2 : 3-Triketohydrindene CsH^^q^CO. 

A substance of this formula was prepared in 
small quantity by Kaufmann (Ber. 1897, 30, 
387) by the oxidation of 1 : 3-diketohydrindene. 
with hydrogen peroxide. The compound pie- 
pared in^this way crystallised from glacial acetic 
acid as brown leaflets which melted and decom- 
posed at I90°-206°. It is probable that the 
substance obtained by Kaufmann possesses 
another structure and that the true triketo- 
hydrindene is the compound prepared by 
Ruhemann, in the form of a hydrate, by the 
action of dilute sulphuric acid on the compound 
formed by the condensation of a-hydrindone 
with p-nitrosodimethylaniline 



/CO 
C.h/ >C:N-C,H,-N(CH 
\!:NC,Ht-N(CH,), 



C.H.<CO>C(OH), 



Tliia reaction can also be applied to 1 : 3-diketo- 
hydrindene and to /3-hydrindone (Chem. Soo. 
Trans. 1910, 97, 1438, 2025 ; 1911, 99, 792). 

Triketohydrindene hydrate forms prisms 
from water wUch redden at 125°, give ofi gas at 
139° and melt with decomposition at 239°-240°. 
The hydrate colours the skin red and reduces 
Fehling's solution. The diphenylhydrazone 
melts at 207°-208° and the disemicarbazone 
darkens at 176° and melts with evolution of 
gas at 208°. 

Triketohydrindene hydrate may be used as a 
reagent for proteins and their hydrolytic pro- 
ducts (ep. Chem. Soo. Trans. 1911, 99, 798). 

J. F. T. 

INDIAN FIRE is a light used in pyrotechnical 
displays and for purposes of signalling. It is 
usually composed of 7 parts of sulphur, 2 of real- 
gar, and 24 of nitre. 

INDIAN HEMP RESIN v. Resins. 

INDIAN INK 01 CHINESE INK. This 
substance, used for writing or drawing, con- 
sists of lamp-black held together with animal 
or fish glue and dried in the form of cakes 
or sticks of paint. According to Chinese writers, 
the invention of ink is due to one Tien-Tchen 
who lived between 2697 and 2597 B.C. It is 
said by them that at that time the ink used 
was a kind of lacquer ; later some kind of black 
stone rubbed in water came into use ; lastly. 



108 



INDIAN INK OR CHINESE INK. 



about 260 years B.C., balls of lamp-black from 
the burning of lacquer and firewood, afterwards 
mixed with size, became the customary material. 
It is probable, however, that the Chinese became 
acquainted with the substance from the Coreans, 
to whom they are indebted for other useful arts. 
The material used for producing the lamp-black 
is in most instances fir timber, although many 
other media, such as rice treated with a decoc- 
tion of Hibiscus miUabilis (Linn. ), the bark of the 
pomegranate tree infused with vmegar, and rock- 
oil are employed. The glue or size appears at the 
present day to be always obtained either from 
oxen or fish; th6 points of difierence between 
various makers being (1) the mode of its pre- 
paration ; (2) the method of incorporation ; and 
(3) the quantity relative to the amount of soot. 
Sometimes perfumed essences, as of musk or 
camphor, are added, especially in the choicest 
qualities. After baking, the sticks or other 
moulded forms are laid in a cool, dry place, and 
are said to improve with long keeping. 

The manufacture of Indian ink is also carried 
on in Japan, the following description, from a 
native source, indicating the method foUowed in 
that country. ' The body of the ink is soot ob- 
tained from pine-wood or resin, and lamp-black 
from sesamum oil for the finest sort. This is 
mixed with liquid ghie made of ox-skin. This 
operation is efiected in a large, round, copper 
bowl formed of two spherical calottes placed 
I inch apart, so that the space between can be 
filled up with hot water to prevent the glue 
from hardening during the time it is being mixed 
by hand with the lamp-black. The cakes are 
formed, in wooden moulds, and dried between 
paper and ashes. Camphor, or a peculiar mix- 
ture of scents which come from China, and a 
small quantity of carthamiiie (the red colouring 
substance of safflower) are added to the best 
kinds for improving the colour as well as for 
scenting the ink.' 

M. Merim^e (De la Feinture k I'Huile) as- 
serted that the Chinese do not use an animal but 
a vegetable size ; but apparently without warrant. 
For a curious monograph compiled from native 
Chinese sources v. L'Encre de C3iine, son Eis- 
toire et sa Fabrication d'aprSs documents 
chinois traduits, par Maurice Jametel, Paris, 
1882. 

INDIAN RED. A mineral pigment from the 
Persian Gulf. In appearance it is a coarse 
powder of a purplish-red colour. 

Howe's analysis of (1) the entire mineral, and 
of (2) that portion soluble in hydrochloric acid, 
gave 

SiOj.I'ejOj.AIjOs.CaO.MgO, SO^COj, HjO 
15 3017 66-59 S-79 2-65 143 228 1-73 l-62=100-26 
;2) — 319 2-22 2-65 087 228 1-78 — =1294 
(Edin. New Phil. Jour. New Series. 2, 306.) 

The portion insoluble in hydrochloric acid 
is a ferric silicate FegOj-SiOj. A pseudo-Indian 
red is composed principally of sesquioxide of 
iron. 

INDIAN YELLOW, PIIHtl, PURREE, os 
PIOURY, is a pigment mainly used in India for 
colouring walls, doors, and lattice work, and by 
artists for water-colour work. On account of 
its disagreeable smell it is but rarely employed as 
a dyestuS. It is made almost exclusively at 
Monghyr in Bengal, and is obtained from the 
urine of cows which have been fed upon mango 



^i 



leaves. On heating the urine, usually in an 
«arthen pot, the colouring matter separates out ; 
this is pressed into a ball and dried partly over 
a charcoal fire and finally in the sun. It sells 
on the spot at about 1 rupee per lb., and is 
mainly sent to Calcutta and Patna. One cow 
produces, on the average, 3-4 litres of urine per 
diem yielding 2 oz. (50 grams) of piuri. The 
yearly production is stated to be from 100 to 150 
cwts., which is probably over-estimated (e. 
Journ. Soc. Arts, 1883, [v.^ 32, 16, and Annalen, 
264, 268). 

Piuri occurs in commerce in the form of 
round balls, which internally are of a brilliant 
yellow colour, whereas the outer layers are either 
brown or of a dirty green colour. The substance 
has a characteristic urinous smell. The unde- 
composed part consists only of ev3:anthic acid 
(CisHijOii) in the form of a magnesium or cal- 
cium salt; the outer and decomposed portion 
contains in addition ewcanthone both free and 
combined. The composition of -piuri seems to 
be variable : a fine sample, according to Graebe, 
contained 

Euxanthic acid . '. . 51 '0 
Silicic acid and alumina , . 1-5 
Magnesium . . , .4-2 
Calcium . . . .3-4 

Water and volatile matter . 39-0 

99-1 
Euxanthic acid is easily obtained by 
digesting piuri of good quality with dilute hydro- 
chloric acid and treating the residue with a solu- 
tion of ammonium carbonate. On the addition 
of hydrochloric acid to the filtered solution 
euxanthic acid crystallises out with IH^O in 
glistening straw-yellow needles, melting at 162°. 
Euxanthic acid is, according to Spiegel, de- 
composed by hydrochloric acid into glycuronic 
acid and euxanthone : 

Ci9Hi30ii = Ci8H804-t-C8Hi„0,. 

Kiilz, in order to prove the animal origin of 
euxanthic acid, gave euxanthone to rabbits 
and dogs, and was able to detect euxanthic acid 
in the urine. Kiilz's experiments did not cor- 
roborate Schmid's statement that mangostin 
(obtained from Oarcinia Mangostana [Linn.]) is 
similarly converted into euxanthic acid by 
animals (E. Kulz, Zeitsch. Biol. 33, 475; 
J. Soc. Chem. Ind. 6, 507). 

Although the potassium and sodium salts of 
euxanthic acid are of the type CigHt,Oj,M, the 
silver salt obtained from the potassium salt by 
silver nitrate has the composition O19H, .O^gAg, 
and is derived from an anhydride of the acid 
{Anhydroeuxanthic acid) ; the methyl and ethyl 
esters prepared from the silver salt are of the 
same type (Graebe, Ber. 1900, 53, 3360). 

Potassium euxanthate Ci,S.nOt^KMiO crys- 
tallises readily from water, and is prepared by 
neutralising euxanthic acid with potassium 
carbonate. 

Magnesium euxanthate C],H„0iiMg,5H:0 
is the main constituent of Indian ydlow (Graebe, 
Annalen, 254, 268). 

Barium euxanthate Ba(Ci9H,,0]i)j,9HjO is 
soluble in boiling water, and on cooling separates 
in the gelatinous condition. 

Silver anhydroeuxanthale CuHisOiQAg be- 
haves similarly. 



INDIGO, NATURAL. 



anhydroeuxanthate CisHjjOjjCjHs, 
yeUow-colonrBd needles, melts at 198°. 
Tefra-acetylethylanhydroeitxantliate 
C„Hi,Oi„C,H,(CaHaO)« 
colourless needles, melts at 216°. 

Melhyl anhydroeuxanthate CijHijOnjCHj, 
melts at 218°, and closely resembles the ethyl 
derivative. 

Benzoyl anhydroevaanthate 

Cj,H„Oi„(CO-CeH5)5 
melts at 194°, but has not yet been crystallised. 
The constitution of euxanthio acid is ex- 
pressed by Graebe (Annalen, 254, 267) as 



OHC.H 






> 



CeHjO CH OHCCHOH), COOH 



whereas for that of anhydro-euxanthio acid the 
following two formulse are given : 
I. 

0HCeH3<f yCjHjO CH^HOH0H(CHOH)3CO2H 
II. 0C5H,<^°>C,H,0 



-i 



!HOH 



be. CHOH 

CH(OH)jCOOH. 

BvaanChone, Purrenone, PumneCiJBifiiWa,B 
first obtained by Stenhouse (Annalen, 61, 425), 
and soon afterwards by Erdmann {ibid. 52, 
365) from euxanthio acid. It crystallises in 
pale yellow needles or laminae, melting at 240° 
(eorr.), which sublime with little decomposition 
on gentle heating. 

Diacdyl euxanihone, pale yellow prisms 
(Salzmann and Wichelhaus, Ber. 1877, 10, 1397), 
melts at 185°. 

By distillation with zinc dust (Salzmann and 
Wichelhaus; Graebe and Ebrard, Ber. 16, 75) 
euxftnthone gives Tnethylenediiphenylene oxide (I.), 
which by oxidation is converted into xanthone (II. ) 

1. 1 1 I ■ J n. 1 I I 1 

indicating that euxanthone possesses the con- 
stitutional formula 

of a dihydroxyxariihone (S. and W.). 

When fused with alkali euxanthone yields 
etixanthonic acid, 

DoA/ 

hydroquinone (v. Baeyer, Annalen, 155, 267), and 
resorcinol (Graebe, ibid. 254^ 266). 

The first synthesis of euxanthone is due to 
Graebe (Z.c), who accomplished this by distilling 
a mixture of ;3-resorcylic acid, and hychroquinone- 
carboxylic acid, and it was shown later by 
Kostanecki and Nessler (Ber. 1891, 24, 3983) 
that if in this reaction the ;8-/esorcylic acid is 
replaced by resorcinol the same product is ob- 
tained. As the result of these syntheses two 




' 109 

constitutional formula for euxanthone were 
possible : 

\Acoa;oh '^^coA;«« 

I. 11. 

When methylated by means of methyl 
iodide in the usual manner (Kostanecki, Ber. 
1894, 27, 1992), euxanthone yields only a mono- 
methyl ether C,3H,0a(0CH,) (yellow plates; 
m.p. 129°), and this on treatment with strong 
sodium hydroxide solution gives an' insoluble 
yellow sodium salt. The latter, by washing 
with water, is decomposed with regeneration 
of the free monomethyl ether. These reactions ' 
indicate that euxanthone contains an hydroxyl in 
the ortho position to a oarboxyl group (cp. also 
Herzig, Monatsh. 12, 161), and that, therefore, 
its constitution is represented by formula II. 
The final proof of this formula is afforded by a 
later synthesis of euxanthone (Ullmann and 
Panchaud, Annalen, 350, 108). 

2-Chloro-6-methoxy benzoic acid is condensed 
with the potassium derivative of hydroquinone 
monomethyl ether, employing copper powder 
as a catalyst. 

OCH, 
/\C00B. , 

i^;ci + 



/\0CH, 



= /\C00H. /\0GH3 

The resulting 4:-methoxy-2-phenoxy-6-methoxy- 
benzoic acid when treated with concentrated 
sulphuric acid is converted into euxanthone 
dimethyl ether 

OCH3 

and this by treatment with aluminium chloride 
in the presence of benzene gives euxanthone, 

Diaazobenzene euxantlume C,sH|,Oi(C,H5N8)a 
(A. G. Perkin, Chem. Soo. Trans. 73, 666), 
red needles; m.p. 249°-250° (decomp.) is 
readily prepared by adding diazobenzene sul- 
phate to a weak alkaline solution of euxanthone. 

AcelyUisazobenzene euxanthone ochre-yellow 
needles, melts at 197°-199°. Euxanthone 
possesses onlyi feeble tinctorial properties ; 
the respective shades obtained with woollen 
cloth mordanted with chromium, aluminium and 
tin being dull brown-yellow, pale bright yellow, 
and very pale bright yellow (Perkin and Hummel, 
Chem. Soc. Trahs. 1896, 69, 1290). A. G. P. 

INDIARUBBERorCAOUTCHOUCi».EiTBBER. 

INDICAN V. Glucosidbs; Indigo, NAitrEAL. 

INDICANORIA v. Indoxyl oompounds. 

INDICATORS V. Acidimetey and Alkali- 
metry ; also art. Analysis. 

INDIGO, NATURAL. Indigo has been known 
in Asia from a remote period of antiquity, and 
there exist very ancient records in Sanskrit 
describing its methods of preparation. 
The Romans appear to have only recognised 
it as a pigment (indicvm), but evidence as 
to its use as a dye by the ancient Egyptians 
has been abundantly proved from the examina- 



110 



INDIGO, NATURAL. 



tion of mummy cloths. Its employment in 
Europe was very limited, until in 1516 it began 
to be impoited from India by way of the Cape 
of Good Hope, though, on the other hand, its 
introduction in large quantity did not occur until 
about 1602. Owing chiefly to the opposition of 
the growers of woad, its European rival, its use 
as a dyeware met with much opposition, and 
various laws were enacted both on the Ck)ntinent 
and in England prohibiting its use. It was, 
moreover, called a • devilish drug,' and was said 
to be injurious to fabrics. In 1737 its employ- 
nient was legally permitted in France, and from 
this period its valuable properties appear to have 
become gradually recognised throughout Europe. 

The most important plants which yield 

indigo are those of the genus Indigofera belonging 

to the natural order of the Leguminosce ; these 

have been cultivated in India, China, Egypt, 

' the Philippines, Caracas, and Brazil. 

For the purpose of indigo manufacture the 
Indigofera Hnctoria (L.), /. sumatrana (Garrtn.) 
(the Indian plant), /. disperma (L.), /. argeniea 
(L.), and /. arrecla (Hochst.) (the Natal plant), 
the /. pauUfolia (Delile) (Madagascar plant), 
and /. aecundiflora (Poir.) (Guatemala plant), 
have been mainly used, though certain less 
valuable varieties, viz. the /. paevdotirwtoria 
(R. Br.), /. angustifolia (L.), /. orcuoto (Willd.), 
/. caroUniana (Walt.), /. c«Jiereo-(Wrild.), Z. 
longeracemosa (Boiv.), /. ecervka (Eoxb.), I. 
- endecaphylla (Jacq.), i. glabra (L.), /. hirsuta (L.), 
/. indica (Lam.), /. mexicana (Benth.), /. lepto- 
stachya (DC), have been employed. In Japan, 
China, and Bussia the plant usually cultivated 
has been the Polygonumtindorium (Ait.), but the 
Isatis tinctoria (L.), or woad plant, at one time 
very largely grown in Europe, is now used in very 
limited quantity as an adjunct in the dyeing of 
indigo (woad vat). The native source of indigo 
in Western Africa appears to consist almost 
entirely of the Lonchocarpas cyanescens (Benth.) 
(Perkin, J. Soc. Chem. Ind. 1907, 26). 

Other indigo-yielding plants are the Nerium 
tinctorium, Qymnema tingens (Spreng.), Eupato- 
riwm laeoe (DC), Tephrosia tinctoria (Pers.), 
Marsdenia tinctoria (R. Br.), and certain species 
of orchids sachaathe Phaiusgrandiflorus (Beich.), 
and CalanChc verairifolia (B. Br.). 

In addition to these various plants of which 
the Mercuridlis perennia (Ldnn.), Fagopyrum 
escidentum (Moench), Fraxinua excelsior (Linn.), 
Baptisia tinctorial^. Br.), and Rhamnus Ala1ernu» 
(L.) (Georgievics, Der. Indigo, 1892) may be given 
as examples, are stated to yield indigo, or a very 
similar colouring matter, but this requires con- 
firmation. 

The production of indigo from the indigo 
plant is of a simple character and consists 
mainly of two processes, viz. a steeping of the 
plant with water (fermentation), followed by the 
oxidation of the solution with air in a separate 
vessel. Until very recently but little modifica- 
tion appears to have been introduced into this 
ancient process, and there is also but little 
variation to be found in the main features as 
described by Bancroft (Philosophy of Permanent 
Colours, 1813), Crookes (Manual of Dyeing 
and Calico Pnnting, 1874). Bridges-Lee (Indigo 
Manufacture, 1892), Georgievics (l.c. 1892), and 
RawBon (The Cultivation and Manufacture of 
Indigo, J. Soc. Dyers. 1899). 



Directly the plants are cut down they are 
tied in bundles and brought to the factory 
without delay, because it is necessary that the 
material should be operated on at once. The 
tanis for the extraction (steeping vats) and pre- 
cipitation of the indigo by oxidation (beating 
vats) are sometimes of stone, but more usually 
of brick- work lined inside with cement, and are 
respectively ranged in two rows one above the 
other, so that the former can be drained ihto 
the latter. The steeping vats may have a 
capacity of about 1000 cub. ft., and are usually 
of much smaller dimensions than the beating 
vats, of which less are consequently required. 
According to Bawson Q,.c.), who describes a 
small indigo factory, each range of beating vats 
runs the whole length of six steeping vats, and 
has a width of 13 feet 6 inches. 

Into each of the upper tanks the bundles of 
tLe plant are tightly packed (preferably in a 
horizontal position, Bridges-Lee, I.e.), on the 
top of this is laid a horizontal trdlis of bamboo, 
and the whole is wedged down into the tanks 
by means of timber, so that the material is 
unable to float during the fermentation process. 
Water is then run in in such quantity that the 
bundles are entirely submerged. After about 
2 hours an active fermentation is observed, and 
the surface of the liquid becomes covered with 
froth owing to evolution of a mixture of carbon 
dioxide, oxygen, and nitrogen (Georgievics, 
I.e.)} in the later stages (Bawson, l.e.) either 
marsh gas or hydrogen oi a mixture of the 
two is freely produced. Aftei 10-15 hours, 
according to the prevailing temperature of the 
water, the straw-yellow, orange, or olive-green 
coloured liquid is drawn oS into the tanks below, 
and submitted to oxidation with air. 

This is accomplished by ' hand beating,' by 
machinery (the beating wheel), by blowing air 
through the liquid, or by the shower- bath method. 
During this operation the coloiii of the liquid 
gradually changes, becoming first dark-green 
and then blue, and considerable frothing is 
produced. When it is observed that the indigo 
precipitate or ' fecula ' readily settles, the 
beating is discontinued and the mixture allowed 
to rest for some 2 hours. The supernatant 
Uquid or ' seet water,' having been drained oS 
as completely as possible, the indigo sludge or 
' mal ' is led into a reservoir inside the factory, 
from which it is subsequently elevated _ by 
means of a hand pump or steam injector into 
a large catddron known as the ' mal boiler.' It 
is here heated by direct fire or by the admission 
of steam, and this has for its object the preven- 
tion of a further fermentation, the solution of 
certain brown impurities, and a more complete 
granulation of the ' mal.' 

The product is then run on to a filter known 
as a ' table,' consisting of stout cotton or linen 
cloth stretched over a shallow rectangular basin 
of stone or cement, with a drainage opening at 
one corner, and allowed to remain until it haa 
the consistency of a stiff paste. In order to 
remove excess of moisture the indigo is trans- 
ferred to perforated wooden boxes lined with 
sail cloth and cautiously pressed. Finally, the 
resulting slab is cut into cakes by means of a 
guillotine or metal wires and allowed to dry at 
the ordinary temperature on trellis-work shelves 
in a specially constructed drying house. 



INDIGO, NATURAL. 



Ul 



The Plant. 
Until the last few years the I. sumatrana 
appears to have been exclusively employed in 
the best-conducted factories in India. Accord- 
ing to Leake (Beport of the Dalsingh Serai 
Research Station, 1903-1904) this is a mixture 
of several sub-varieties of different values. -In 
this, as in apparently all other indigo plants, 
the indican exists exclusively in the leaf, though 
Bloxam and Leake {l.c.) point out that the 
midrib or rachis also contains the glucoside. 
For the manufacture, of indigo the main 
points in connection with the plant are the 
weight of plant yielded per ^acre, the per- 
centage of leaf given by the plant, and the 
indigotin producing value of the leaf. Accord- 
ing to Bawgon (Cultivation and Manufacture of 
Indigo, l.c.) the good plant contains 40 p.c. of 
leaf, though occasionally, but not often, the 
proportion of leaf rises to as much as 60 p.c. 
Bloxam and Leake have found, however, much 
higher values, 61 -7-61 -6 on ordinary Indian 
plant, and 65 p.c. given by twelve experimental 
plots, figures which include the rachis. Berg- 
theil (Beport of the Indigo Besearch Station, 
Sirsiah, 1906, 8) finds the percentage of leaf to 
be 40 p.c., and never higher than 45 p.c. ; but, 
on the other hand, in a redetermination, Leake 
(J. Soo. Chem. Ind. 1907, 26, 1174) records the 
value as 62-2 p.c. Bawson, who conducted 
numerous analyses of the leaf by his persulphate 
process {l.e.), shows that the indican content 
as expressed by indigo yielding capacity varies 
at different periods of the year. Thus, whereas 
in one instance on May 28 the figure was 0-20 p.c, 
on August 25 this had risen to 0-76 p.c. of 
indigotin. Though the leaf on young plant gives 
but a small percentage of colouring matter, yet 
as the plant grows, the new leaf contains more 
colouring principle than the old on the same 
plant. As an example, on one occasion the 
percentages of indigotin recorded with new and 
old leaf were respectively 0'71 and 0-35 p.c. 
Finally, there is a gradual increase in colouring 
matter given by leaves from the bottom of the 
plant upwards as . represented by the figures 
0-30, 0'44, and 0-62 p.c. respectively. According 
to BergtheU (Beport of the Indigo Besearch 
Station, 1907, 3) the ' indigotin content ' of the 
plant is rarely so high as 0-3 p.c. Though the 
leaf, as a rule, contains a maximum of colouring 
matter from about the middle to the end of 
August, it does not necessarily follow that this 
is the best period for manufacture, as by this 
time the plant will usually have lost a consider- 
able portion of leaf (Bawson). The manufacture, 
indeed, usually commences about the middle of 
June. Gaunt, Thomas, and Bloxam (J. Soc. 
Chem. Ind. 1907, 26, 1174) refer to a; sample of 
the air-dried leaves of the /. sumatrana, which, 
in comparison with other dry samples of the same 
variety (0-6 approz.) and of the Java plant /. 
arrecta (1'81 p.c.) yielded indigotin to the value 
of 3-63 p.c, and consider that this indicates 
that by selection and suitable methods of 
cultivation it should be possible to obtain an 
average plant of greater indigo producing power 
than has hitherto been the case. 

The plant formerly employed by the Java 
planters was the Indigofera aecundifiora ' Guate- 
mala plant,' but for several years past this has 
been replaced by the /. arrecta or ' Natal plant.' 



The latter, it is stated, contains not only more 
leaf than the ordinary Indian plant, but, as a 
rule, the leaf yields also a considerably larger 
percentage of indigo. More recently the Indian 
planters have recognised the value of the /. 
arrecta, and accounts are given by Coventry 
(Indigo Improvements Syndicate Report, .1901) 
of experiments in connection with its introduction. 
Leake (Dalsingh Serai Report, 1905) discusses 
the difficulties of the germination of the seed 
of the Natal-Java plant, which is due to the 
impermeable character of the seed coat. This 
defect, it is pointed out, can be overcome by 
a process of scratching, and a practicable method 
for this purpose is described. Bergtheil (I.e.), 
in conjunction with D. L. Day, treats the seed 
with strong sulphuric acid , which leads either to a 
BweUing of the seed coat and its eventual rupture 
or converts it into a body akin to cellulose and 
permeable tq water. Analyses of the indigo- 
yielding power qf this leaf by Rawson (2.c.)^ 
gave figures up to 0-96 p.c, whereas Bergtheil 
(I.e. 1906) finds in comparison to the/, sunuarana 
(0-685) that the /. arreeta produced 1-06 p.c. of 
colouring matter. The percentage of leaf 
given by the latter averages 62-2 p.c. Again in 
1909 the yield from 100 maunds of the /. 
arrecta was 15 seers 10 chfttacks, as against 
11 seers 14 chittacks from the same quantity 
of the I.' sumatrana. The Natal plant is now 
established in India, and its superiority over the 
Indian plant is fuUy recognised. According to 
Bergtheil (1907) the indigo made from the Java 
plant has generally been of a high indigotin 
content, and (1906) that whereas the yield of 
indigo per acre was 12-6 ' seers,' that given by 
the /. sumatrana was by couvparison only 8 seers. 
A full account of much detailed work on the 
cultivation of the indigo plants by Bawson, 
Bloxam and Leake, and Bergtheil is given in the 
reports above enumerated (o.p. also Bergtheil, 
ibid. 1908-1911). 

The Chemistby of Natural Indioo 

MANnFACTURB. 

According to the early researches of Chevreul 
(Ann. Chim. Phys. 1808, 66, 8, and 1808, 68, 284) 
and of Geradin and Preisser (J. Pharm. Chim. 
1840, 26, 344) the colouring principle of indigotin 
present in indigo-yielding plants was considered 
to consist of indigo wliite, and this theory 
remained uncontradicted until Schunok (Fhil. 
Mag. 1855. [iv.] 17, 74, and 1858, 15, 127) 
isolated from the leatis tinctoria (woad). Poly- 
gonum iinctorium and Indigofera tinctoria 
(Schunck and Eoemer, Ber. 1879, 12, 2311), a 
glucoside, which was named indican. 

To prepare this substance from woad the 
leaves were extracted with cold alcohol, the solu- 
tion treated with a little water, and concentrated 
at the ordinary temperature by blowing air over 
it. The waxy matter which thus separated was 
removed by filtration, and the filtrate shaken 
up with freshly precipitated cupric hydroxide. 
The mixture was filtered, the liquid freed from 
dissolved copper by means of sulphuretted 
hydrogen, and- then evaporated at the ordinary 
temperature. The residue was extracted with 
cold alcohol, the extract treated with ether to 
precipitate certain impurities, and the solution 
evaporated. 

Thus obtained it consisted of a yellow or 



112 



INDIGO, NATURAL. 



yellowish-brown syrup, which was of an exceed- 
ingly unstable nature, and could not be dried 
without decomposition. With alcoholic lead 
acetate it gave a yellow precipitate, whereas in 
aqueous solution it could only be precipitated 
by means of basic lead acetate. Analyses of 
the lead compound indicated that it possessed 
the formula CasHjiNO,,. Schunok found that 
this compound was a glucoside, and that by the 
action of dilute acids, alkalis and of a ferment 
present in the plant, it was readily hydrolysed 
with the formation of indigotin, and a sugar 
indiglucin 
2CseH3,Oi,-N+4H20=C„Hi„OjN,+6C6H,oO, 

For the production of indigotin the presence 
of air 01 other suitable oxidising agent was 
however necessary, and it appeared, therefore, 
that during the reaction the indigotin at first 
formed was reduced to indigo white. 

Later, however, Schunck and Boemer showed 
(2.C.) that indican, when hydrolysed in the 
absence of air, gave a product which, on subse- 
quent treatment with oxidising agents,- did not 
yield indigotin. Schunok further obtained by 
the action of cold dilute acids on his indican a 
brown powder, from which he isolated six 
distinct substances, viz. indihumin, indifjascin, 
and imZirctJM, soluble In warm sodium hydroxide 
solution, and a- and 0-indifulvins and indirubin, 
insoluble in alkalis. 

When aqueous solutions of the indican were 
boiled or heated for some time a decomposition 
ensued, and the product, on treatment with acid, 
gave indiglucin, but no indigotin, this being 
replaced by indiretin and indihumin brown 
amorphous substances. The latter closely re- 
sembled, and was probably identical with, indigo 
brown. By the action of alkalis or alkaline 
earths at the ordinary temperature, indican was 
converted into a new glucoside indicanin 
C2oH2,NO,2, which on treatment with acid gave 
indiglucin and indirubin. 

Oxyindicmin, a brown gummy substance, 
insoluble in alcohol, was isolated during the pre- 
paration of Indican, and yielded, under the 
Influence of acids, indiglucin and a brown 
substance similar to indifuscin. 

MarclUewski and Badclifie (J. Soc. Chem. 
Ind. 1898, 17, 434), in a theoretical discussion 
of the subject, suggested that indican C, ,H, ,OjN 
was a glucoside of indoxyl the hydrolysis of 
which could be represented by the following 
equation : 

Ci4H„O.N+HaO=C,H,ON-)-CeH,A- 
As a result of the communication of March- 
lewski and BadclifTe, Hazewinkel, the director 
of the experimental station for indigo, Klalten, 
Java (Proc. K. Akad. Wetensch. Amsterdam, 
1900, 2, 612), gave an account of a research^ 
concluded in 1898, which he had hitherto con- 
sidered to be to the interest of the Java planters 
to keep secret. In this important paper he 
gives proof for the first time that indican is an 
indoxyl glucoside, and that the sugar obtained 
from it is dextrose. 

The elaborate researches of Beyerinck, van 
Bomburgh, and other Dutch chemists, proved 
that the indican present in the various Indigo- 
feroe and in the Polygonum tinctorivm was far 
more stable than Schunck supposed, and the 
experiments of these authors eventually led to 



the isolation of this glucoside in a crystalline 
condition from the Jndigofera leptoatachya 
and Polygonum tinctorium by Hoogewerff and tet 
Meulen (Proc. K. Akad. Wetensch. Amsterdam, 
1900, 2, 520). 

The leaves were immersed in two and a half 
times their weight of boiling water, boiled for a 
few minutes, and further systematically ex- 
hausted. Without any sensible decomposition 
the decoction could be evaporated in vacu6 if 
care was taken to keep the reaction alkaline. 
The dry residue was extracted with methyl 
alcohol, and to the solution ethei was added as 
long as a precipitate was formed. This was 
removed, the clear liquid evaporated, the 
residue completely dried in vacud, and then 
dissolved in water. The filtered ^nd concen- 
trated solution deposited on cooling well- 
defined crystals of indican. This process may 
be modified by treating the decoction of the 
leaves with baryta water before concentration, 
by which means a large proportion of the 
impurities are precipitated. 17 kilos, of the 
leaves of Polygonum tinctorium yielded 5 grams 
of pure indican. 

Thus obtained indican C,4Hi,05N crystal- 
lises from water in spear-shaped crystals, which 
contain 3 molecules of water of crystallisation. 
Heated in a test tube, or on platinum foil, 
purple-coloured fumes are given oS, but this 
does not take place in an atmosphere of carbon 
dioxide. By passing a current of air through a 
hot solution of indican in dilute hydrochloric 
acid containing a little ferric chloride, 91 p.c. 
of the indican was converted into indigotin 
according to the equation 

2C.4H„NO,+Oa=C,sH,oN20,,-t-2CeH,A- 
There was no difEerence between the indican 
prepared from Xhe /. leptostachya and that ob- 
tained from the P. tinctorium. 

In a paper by Beyerinck (Proc. K. Akad. 
Wetensch. Amsterdam, 1900, 3, 101), 'On the 
Formation of Indigo from Woad,' this chemist 
discusses, Schunck's well-known work on %h.e 
same suliject, and points out that the indigo- 
yielding substance contained in this plant is 
not as Schunck regarded it, identical with the 
indican present in the Polygonum tinctorium. The 
colouring principle of woad Beyerinck names 
isatan, and shdws that this compound, unlike 
indican, is decomposed in feebly alkaline solu- 
tions, whereas indican is stable even in concen- 
trated alkaline liquids. In presence of acids both 
isatan and indican are hydrolysed, but indican 
with greater difficulty. Isatase, the specific 
enzyme of woad, does not act on indican, and 
isatan, on the other hand, is unaffected both by 
the indigo enzyme or by common bacteria. 

Schunck (Chem. News, 1900, 82, 176) con- 
sidered that the crystalline indican of Hooge- 
werff and ter Meulen was not the substance 
obtained by him, and should not be considered 
as a pure variety of it, but was rather derived 
from it, by extracting the plant with a hot 
solvent and the use of chemicals. He preferred 
to name his compound a-indican and theirs b- 
indican. 

Bergtheil (Chem. Soo. Trans. 1904, 86, 877), 
who experimented with the I. eumatrana and 
/. arrecta, did not find it possible to prepare 
indican from the leaves of these plants in the 



INDIGO, NATURAL. 



113 



mannei deaoiibed by Hoogewerfi and ter 
Meulen. 

It waa, however, shown by Parkin and 
Bloxam (Chem. Soo. Trans. 1907, 91, 1715) that 
crystalline indican can be isolated from both 
o{ these plants by such a method, and is in 
reality the source of the natural indigo which is 
derived from them. 

In a further communication ter Meiilen 
(Bee. trav. chim. 1905, 29, 444) describes a 
modification of the method previously given for 
the isolation of indican from the Polygonum tine- 
torium, which consists in treating a cold solution 
of the partially purified substance with sulphuric 
acid, by which means certain impurities are pre- 
cipitated. The acid is then removed with barium 
carbonate. The main object of the investigation 
was, however, the determination of the sugar 
that this glucoside yields when hydrolysed by 
its specific enzyme, and this proved to be dex- 
trose, as already indicated by Hazewinkel {l.c.). 

As a result of the study of the behaviour of 
indican with solvents, Ferkin and Bloxam {l.e.) 
devised a very simple process for the isolation of 
this glucoside, by the aid of which large quantities 
of the pure substance could be readily prepared. 

The leaves and stems of the /. sumatrana 
(1000 grams) were treated with 4 litres of cold 
acetone, the mixture being occasionally shaken 
during 7 days, and the green-coloured extract 
was evaporated on the steam bath to a very 
small bulk. To the residue light petroleum 
was added, causing the deposition of a brown 
viscous precipitate of crude indican, and this 
was repeatedly agitated with small quantities 
of light petroleum. The product on treatment 
with water gave a pale yellow liquid, containing 
resinous matter in suspension, and the latter was 
removed by shaking with ether. The clear 
aqueous solution, treated with 10 c.c. N/2 
sodium carbonate, on gradual evaporation in 
vacv6 deposited crystals, and eventually a 
semi-solid mass was obtained. It was collected, 
drained, and allowed to dry at the ordinary 
temperature. .When exhaustively extracted, 
1000 grams of leaf gave 31 -66 grams of indican, 
and by a continuous system of worldng more than 
600 grams of crystalline indican were prepared. 
The preparation of this glucoside from the leaves 
of I. arrecta is more troublesome, owing partly 
to the presence of ksempferitrin, but more 
especially of a colourless sugar-like compound 
CjHijOs ; m.p. 186°-187'' ; possibly a modifica- 
tion of quercitol. The fact that indican can be 
30 readily isolated without the aid of heat, and 
merely with the use of acetone, light petroleum 
and ether, is not in harmony with the contention 
of Schunck ({.c.) that the crystalline glucoside 
is an alteration product of his amorphous 
substance, and consequently the terms o- and 
^-indican suggested by him should disappear. 
Indican crystallised from water 
C,.H„0,N,3H,0 
melts at 57°-58°, but in the anhydrous condition 
as obtained by the addition of boiling benzene 
to its hot alcoholic solution, at 176°-178°. 
Owing to its somewhat ready solubility in water 
it can be more economically purified by the 
latter process, and, according to Ferkin and 
Thomas (Chem. Soo. Trans. 1909, 95, 793), 
crystallisation from absolute alcohol gives 
excellent results. 

Vol. hi.— T. 



It has been shown by Baeyei (Ber. 1881, 1^, 
1745) that indoxyl readily condenses with alde- 
hydes and ketones to form the so-called iniogen- 
idea, and Hazewinkel (2.C.), in the valuable 
communication which demonstrated for the first 
time that indican is an indoxyl glucoside, 
partly identified this substance by means of its 
condensation products with isatin, benzaldehyde, 
and pyruvic acid, relying, however, on taeir 
qualitative reactions, as he did not prepare 
these compounds in a pure enough condition 
for analysis. Almost simultaneously Beyerinck 
(Froc. K. Akad. Wetensoh. Amsterdam, 1899, 
2) 120) prepared indirubin by hydrolysing crude 
indican in the presence of isatin. 

Ferkin and Bloxam (i.e.), and Gaunt, Thomas, 
and Bloxam (J. Soo. Chem. Ind. 1907, 26, 1174), 
who experimented with the pure substance, 
found that when indican dissolved in water is 
added to a boiling solution of isatin, acidified 
with a little hydrochloric acid, and the operation 
is carried out in an atmosphere of hydrogen or 
carbon dioxide, the yield of indirubin is 
quantitative according to the following equa- 
tions : — 

C,.H„O.N-l-HjO = C.H,NO-f C,H„0,. 

C8H,NO-t-C,H5NOj = C„H,„N,0,-f-H,0. 
This* isatin 'method, for full details of which 
the original papers must be consulted, affords a 
ready means, not only for the analysis of the 
crystalline glucoside, but also for the estimation 
of the amount which is present in aqueous 
infusions of the leaf (v. infra). 

More recently Ferkin and Thomas (Chem. 
Soo. Trans. 1909, 96, 795), who studied in a 
similar way the condensation of indoxyl derived 
from indican with p-nitrobenzaldehyde, found 
that the p-nitrobenzaldehydeindogenide is de- 
posited in quantitative amount, and that this 
reaction could also be employed for the analysis, 
both of c/ystaUine indican and that present 
in the leaf extract. The reaction takes place 
with extreme readiness, for with indican solu- 
tion at a dilution of 1 in 1000, the above 
compound quickly separates, and even at 1 
in 10,000 the condensation can be observed 
to take place. F^peronal and indican in the 
presence of dilute acid yield the analogous com- 
pound CibHiiOjN, orange-coloured needles; 
m.p. 223°- 224°, but this process, under analytical 
conditions, gave only approximately satisfactory 
results. Ab a side issue, p-hy droxy benzaldehyde- 
indogenide C,5H,,0,N orange-red needles, 
m.p. 267°-269°, and dihydroxybenzajdehyde- 
indogenide OijHuOjH orange-red needles, m.p. 
264°-265°, were prepared from indican. The 
latter compound derived from protocatechuio 
aldehyde dissolves in concentrated sodium hydr- 
oxide, with a bluish-violet colouration, and dyes 
with mordanted woollen cloth well-defined 
shades. 

On the other hand, when indican is hydrolysed 
with acid in the presence of an oxidising agent 
it does not appear possible to obtain a quanti- 
tative yield of indigotin. Hazewinkel (i.e.) 
states, in regard to this point, that acid oxidising 
agents convert indican into indigo, and this in 
turn is oxidised by an excess of the reagent. 
By the use of ferric chloride and hydrochloric 
acid, Hoogewerff and ter Meulen obtained from 
the pure glucoside only 91 p. c. of the theoretical 
quantity of colouring matter, which appeared 



114 



INDIGO, NATXJRAIi. 



to contain indirubin, and was of doubtful purity. 
Gaunt, Thomas, and Bloxam (!.e.),who examined 
the behaTioni of ammonium persulphate, a 
reagent suggested by Rawson for the analysis 
of the plant extract (Report on the Cultivation 
and Manufacture of Indigo, Mozzufferpore, 
1904; cp. also Bloxam and Leake, Dalsingh, 
Serai Report, 1904), found that the process 
was far from quantitative with pure indican, 
and that the yield of colouring matter 
averaged but 82 p.c. of the theoretical. 
Perkin and Thomas (he.) studied the effect 
of the hydrolysis of solutions of indican with 
acid during the aspiration of air through the 
liquid, under varying conditions of tempera- 
ture and concentration. The most satisfactory 
yield of pure colouring matter (93'5 p.c.) was 
produced when air was passed during 8 hours 
through a solution of 0-6 gram of the glucoside 
in 850 c.c. of water acidified with 15 c.c. of 33 p.c. 
hydrochloric acid, and the temperature main- 
tained at 60°. 

When, however, the operation was carried 
out at 70° less colouring matter was obtained 
(87-6 p.c), and, curiously enough, replacement of 
the hydrochloric acid by an equivalent amount 
of sulphuric acid, gave under similar conditions, 
a much lower result. The deficiency in the 
yields given by these air oxidation processes 
was due to the fact that a portion of the indoxyl 
had been converted into substances other than 
indigotin, and it was observed that whereas in 
the case of hydrochloric acid the filtrate possessed 
a pale yellow colour, that containing sulphuric 
acid had a browner and darker tint. Indimbin 
was also present in these indigo preparations. 

Whereas Schunck (2.C.) had described the 
production of various brown substances by the 
action of dilute acids on hia indican, and Schunck 
and Roemer (2.c.) had obtained a brown-yellow 
compound by means of hydrochloHo acid in 
absence of air, the behaviour of the pure crystal- 
line glucoside in this respect was studied by 
Ferkin and Bloxam. When 100 c.c. of a 4 p.c. 
solution of indican was treated with 3 c.c. of 
sulphuric acid, and digested at a boiling tempera- 
ture, the liquid, at first yellow, became brown, a 
brown resinous substance, together with a little 
indigotin, quickly separated, and the presence 
of indole was observed. ~The product of the 
reaction was almost identical in weight with 
that required by the amount of indozyl which 
the glucoside would yield on hydrolysis, and 
consisted chiefly of a dark reddish-brown 
powder (a), sparingly soluble in alcohol, together 
with a small quantity of a similar, though more 
readily soluble substance (&). Analyses of (a), 
whiph is termed indoxyl broum, gave C=68-10 ; 
H=4'10; N=9-34, figures almost identical 
with those found by the same authors for the 
main constituent of indigo brown, and though 
these two products difEec from one another 
in certain minor respects, there could be no 
doubt that they were closely allied. The more 
readily soluble substance (6) also closely re- 
sembled the indozyl brown, and gave on analysis 
N=9-65 p.o. Indican, when treated with cold 
hydrochloric acid in - the absence of air, for 
90 hours, gave indoxyl brown and a soluble 
brown substance similar to that described 
above (Perkin and Thomas). The acid filtrates 
from the indozyl brown preparations contained 



dextrose, and this was identified by means of its 
osazone, and also by the preparation of its 
acetyl derivative. 

The Indigo enzyme discovered by Schunck 
{l.c.) has been elaboratdy investigated by the 
Dutch chemists. Beyerinck (Proc. K. Akad. 
Wetensch. Amsterdam, 1899, 1, 120) extracts 
the finely divided leaves of the plant, first 
with cold 96 p.c. alcohol, and subsequently 
with more dilute alcohol, which removes chloro- 
phyll, indican, wax, &c., and leaves a snow-white 
highly active powder. From such preparations 
the enzyme itself was only imperfectly re- 
moved, for in water it is almost insoluble, only 
sparingly so in glycerol, and rather more readily 
in 10 p.c. solutions of sodium and calcium 
chlorides respectively. The residue _ which re- 
mains after extraction in this way is not per- 
ceptibly less active than before treatment. A 
minute study of these leaf preparations was 
carried out by Beyerinck in regard to their 
behaviour with partly purified indican solutions, 
and he indicates the effect of temperature on 
the intensity of the hydrolysis by means of 
curves. Among numerous points of interest it 
was observed that ammonia quickly destroys 
the enzyme, and also that emulsin slowly 
hydrolyses indican, although the intensity of its 
action was only one twentieth of that of 
Indigofera enzyme preparations. 

Hazewinkel {ibid. 1900, 2, 613), who 
investigated the subject in 1898, arrived in- 
dependently at Beyerinck's conclusions. By 
means of lus enzyme preparation he proved for 
the first time that indican is a glucoside of 
indozyl. Finding that emulsin also acted on 
indican solutions he called the indican enzyme 
indimvlsin, and considered that a 10 p.c. 
solution of sodium chloride is the best medium 
for dissolving it. A very interesting point 
which he mentions is that during fermentation 
no indican passes from the leaf into the 
surrounding liquid. 

In the paper of van Bomburgh (ibid. 1899, 
2, 344) allusion is made to the insoluble character 
of the enzyme, and to the activity of emulsin 
with solutions of indican. Finally, Beyerinck 
{ibid. 1900, 3, 101) demonstrated that the 
ferment present in woad, Isatis tinctoria, is not 
capable of hydrolysing indican, though itreaots 
with isatan, the peculiar indigotin yielding 
principle of this plant. BergtheU (Chem. See. 
Trans. 1904, 85, 877), whose paper covers 
ground already traversed by Hazewinkel, 
Beyerinck, and van Romburgh, considers that 
the difBciilty- which occurs in extracting the 
enzyme is due to the presence of tannin in 
the leaves {cp. Brown and Morris, Chem. Soo. 
Trans. 1893, 63, 604). Bjr pounding the leaves 
with hide powder the tannin becomes fixed, and 
a very active solution of the enzyme can be 
obtained. 

Ter Meulen (Bee. trav. chim. 1905, 24, 444) 
is, however, in agreement with the other Dutch 
work referred to above, as is evident from his 
statement ' L'enzyme de i'indigo est insoluble 
dans I'ean.' According to Gaunt, Thomas, and 
Bloxam (2.c), Bergtheil's product is not a true 
solution, as the enzyme is entirely removed from 
it by means of a Berkf eld filter. Thomas, Perkin, 
and Bloxam (Chem. Soc. Trans. 1909, 35, 829) 
again point out that there is no certainty of the 



INDIGO, NATURAL. 



presence of tannin in the leavea of the /. 
sumatrana and I. arrecta, and that any tannin 
matter if originally present would be eUminated 
daring the repeated extraction of the material 
with alcohol. As the result of their experi- 
ments the insolubility of the enzyme was con- 
firmed. 

A study of the hydrolysis of pure indican by 
means of the enzyme and subsequent oxidation 
of the indoxyl solution with air under varied 
conditions has been made by Thomas, Perkin, 
and Bloxam {l.e.). The fermentation was 
carried out in an atmosphere of purified hydro- 
gen, and the temperature and dilution of the 
solution in both this and the subsequent oxida- 
tion process were so arranged as to fairly approxi- 
mate the ordinary factory routine. For full 
details of apparatus and the .analytical pre- 
cautions adopted the original paper must be 
consulted. , 

The results of this investigation show that 
the hydrolytic action of the enz3rme proceeds 
somewhat rapidly, and that by employing 2 grams 
of the enzyme and I gram of indican under the 
conditions of dilution stated, the reaction was 
complete after 2 hours' digestion at 60°. The 
solution, though free from indican, contains, 
however, less than the theoretical amount of 
indoxyl (93 p.c.). This is due to the fact that 
some quantity of the indoxyl (4 p.c.) is occluded 
by the enzyme powder, and it was found that by 
increasing the quantity of this latter a corre- 
spondingly greater loss occurs. The residual 
deficiency (3 p.c. approx.) arises from the 
instability of indoxyl itself, which even in an 
atmosphere of hydrogen at 50° is slowly con- 
verted into a product which ia incapable of 
giving indigotin on oxidation. This property, 
which is referred to as the ' decay ' of indoxyl, 
is much more evident when the digestion with 
the ferment is prolonged for several hours, and 
the experiments of these authors indicate that 
by such a treatment for 30 hours, at least 
20 p.c. of the indoxyl undergoes this transforma- 
tion. On the other hand, at 15°, in an atmo- 
sphere of hydrogen, the indoxyl solution is com- 
paratively stable, and on standing for 24 hours, 
had experienced a loss of only 3 p.c. 

According to Beyerinck (J.s.) great attention 
should be paid to the degree of the acidity of 
indican solutions which are undergoing fermen- 
tation, and this is corroborated by Thomas, 
Perkin, and Bloxam. Thus, by the presence of 
a trace of sulphuric acid during the fermenta- 
tion, the decay of the indoxyl is practically 
inhibited, and, moreover, by the addition of a 
further quantity of the acid at the close of the 
operation, the occlusion of the indoxyl by the 
enzyme powder is also prevented. As a result 
of this procedure the solution contained 99-5 p.o. 
of the theoretical quantity of indoxyl. 

When a dilute aqueous solution of indoxyl 
is oxidised by air the reaction is more complex 
than has usually been considered the case, and 
a quantitative yield of indigotin is not pro- 
duced. Thomas, Perkin, and Bloxam have, for 
instance, found that the indoxyl solutions 
produced by the enzyme hydrolysis of indican, 
when treated with aii at 60°, gave only 
88 p.c. of the theoretical quantity of indigotin, 
admixed with a little indirubin. It thus appears 
evident that in addition to the oxidation of 



118 

indoxyl to indigotin some secondary reaction 
occurs, but of the chemical nature of this change 
there is as yet no certain evidence. The isola- 
tion from the indigo thus produced of traces of 
substances resembling indoxyl brown or indigo 
brown indicates the effect, at least in part, of a 
condensation similar in character to that which 
is involved in the production of the former pro- 
duct. Moreover, the filtrate from the incUgo, 
which is prepared in this manner, was invariably 
of a dull yellow colour, and yielded, by extrac- 
tion with ether, a small quantity of a yellowish- 
brown resin. , 

This secondary change of indoxyl is facili- 
tated by the presence of potassium acetate in 
the liquid during the oxidation, for by this 
means the yield of indigotin was decreased to 
81 p.c, and the filtrate obtained from it possessed 
a rich dichromate colour. It has long been 
known that the oxidation of indoxyl solutions, 
in so far as the crude fermented factory liquid 
is concerned, is facilitated by the presence of 
ammonia or lime water, and the subject has 
been discussed by Rawson and by Beyerinck 
{l.c. ). According to Thomas, Perkin, and Bloxam, 
the employment of a small quantity of either of 
these reagents during the oxidation of the in- 
doxyl derived from pure indican was beneficial, 
and an increase of about 5 p.c. in the yield of 
indigo thus took place. On the other hand, the 
addition of only a trace of these compounds is 
advisable, because should an excess be present 
the amount of indigo produced is rather de- 
creased than increased thereby. 

But whilst both ammonia and lime water 
in suitable amount partially inhibit the 
secondary change of the indoxyl referred to 
above, a third factor, well known to manu- 
facturers, comes into play, which is repre- 
sented by the production of notable amounts of 
indirubin. For the formation of this colouring 
matter isatin is necessary, and it is likely that, 
in the presence of a large amount of the above 
reagents, an excessive production of this sub- 
stance occurs, and occasions the decreased yield 
of indigo which, under these circumstances, 
has been shown to take place. It h&s, in fact, 
been pointed out by Perkin (Chem. Soc. Proc. 
1907, 23, 30) that traces of isatin exist in Java 
indigos, which are rich in indirubin. 

Curiously enough the presence of a trace of 
hydrochloric acid during the oxidation acts 
in the same manner as ammonia, though to a 
less extent, in increasing the yield of colouring 
matter, but in this case the reaction proceeds 
much less rapidly. The employment of pure 
oxygen with neutral solutions of indoxyl gives 
3-4 p.c. less colouring matter than is obtained 
when air alone is employed, whereas in presence 
of ammonia the yield is but little affected. The 
addition of Chile saltpetre to the fermentation 
vat has been a custom of Indian planters for 
some time, and Rawson (Report on the Cultiva- 
tion and Manufacture of Indigo, 2nd ed., 1907) 
states that although no increase of colouring 
matter is thus produced in the oxidation vat, 
the precipitate settles better. The laboratory 
experiments of Thomas, Bloxam, and Perkin 
with pure indican corroborate this statement. 
Finally, there is but little difference in the yield 
of colouring matter experienced when the 
solution of indoxyl is oxidised by aii at (»ther 



116 



INDIGO, NATURAL. 



30° or 60°, although, if anything, the advantage 
is in the case of the higher temperature. 

As a result, therefore, of the employment of 
(ioid during the enzyme hydrolysis of indican, 
and oxidation of the resulting indoxyl solution 
under feebly alkaline conditions, the best 
yields of colouring matter have been obtained. 
On the other hand, it has not been found possible 
either with synthetical indoxyl or indoxyl 
derived from indican to obtain a quantitative 
yield of pure indigotin or of an admixture of 
this colouring matter with indirubin. In 
regard to the bearing of this work on the com- 
mercial process, Thomas, Ferkin, and Bloxam 
suggest that the effect of the addition of a small 
quantity of srdphuric or oxalic acid to the fer- 
mentation vat should be studied. They consider, 
however, that the most satisfactory laboratory 
results on the preparation of indigotin from the 
plant extract, or from pure indican, are given 
when the solution is hy&olysed by hydrochloric 
acid, with simultaneous oxidation by ail. The 
cost of hot water extraction of the plant is, 
however, considered by Rawson to be prohibi- 
tive. 

Bacterial fermentation. Though in the 
manufacture of indigo, hydrolysis of the indican 
is mainly due to the action of its specific enzyme 
indimulsin, it is well known that the bacteria 
which are present exert a similar although minor 
effect. 

In 1887 Alvarez (Ckimst. rend. 115, 286} 
isolated bom an extract of the indigo plant, 
an organism Bacillus indigogenvs, which was 
capable of producing this fermentation. Beye- 
rinck (I.e.), who studied the matter in consider- 
able detail, points out that a similar effect is 
produced by infecting indigo plant infusions 
with garden soU, and that in this case the 
common gas-producing bacteria perform the 
chief part. Alvarez, he suggests, went too far in 
insisting on the existence of a specific bacterium 
in indigo fermentation. On the other hand, 
Bergtheil {l.c.) considers that at least one 
organism capable of producing indigo fermenta- 
tion is invariably found in large quantities in an 
infusion of the plant. This corresponds very 
closely with the description given by Alvarez of 
his Bacillus indigogentis, and is no doubt identical 
with it. 

Mahufactuee of Indiqo. 

Water. Pure water in large quantity is 
necessary for the manufacture of natural indigo 
(Crookes, Handbook of Dyeing and Calico- 
I^nting, 1874 ; Indigo Manufacture, Bridges- 
Lee, 1892 ; Rawson, Report on the Cultivation 
and Manufacture of Indigo, 1902). When such 
is not available, Bridges-Lee recommends its 
purification, if hard, by treatment with lime 
water, and should much organic matter be 
present by the use of permanganate. Rawson 
also lays stress on this point, and recommends a 
similar method of procedure. In special circum- 
stances the employment of aluminoferrio is 
advisable (Bergtheil, 1909). As the duration 
of the fermentation varies with the temperature 
of the water, Rawson recommends, in case this 
should be lower than 90°F., a preliminary 
heating in the reservoir. 

Fermentation. The duration of this process 
is given by Crookes (2.c.) as 9-H hours, according 



to the prevaiUng temperature of the water, 
whereas Georgievics (Der Indigo, 1892) suggests 
18 hours when the external temperature is 
35-6°C. In very hot weather the fermentation 
is completed in 6 hours. According to Rawson 
(2.C.), when the temperature of the fermentation 
vat is from 90°-92°I'., a 12 hours' steeping gives 
the best result in the case of the /. sumatrana ; 
whereas Bergtheil (Indigo Research Station, 
Sirsiah, 1906) is of opinion that a 10 hours' 
fermentation is sufficient. With the /. arreda 
the steeping should vary from 13 to 15 hours at 
90°, according to the indican content of the 
plant. In other respects, according to Rawson 
and Bergtheil, there is practically no improve- 
ment necessary in the steeping operation as 
carried out in well-managed factories. The 
addition of such chemicals as mercuric chloride, 
sodium and potassium carbonates, lime, carboUc 
acid, formaldehyde, and sugar are not of advan- 
tage, although sodium nitrate, which has been 
employed by planters for many years past, may 
facilitate the deposition of the indigo in the 
oxidising vat. On the other hand, the work of 
Thomas, Bloxam, and Ferkin indicates eis bene- 
ficial the curtailment, as far as possible, of the 
Steeping operation, and the addition of sulphuric 
or oxalic acid in small quantity to the vat as 
advantageous. 

Hot-water extraction. The extraction of the 
indigo plant with hot water has been employed 
for many years, and in Bancroft's Philosophy 
of Permanent Colours, an account is given by 
Dr. Roxburgh, dated 1797, of such a method: — 
' The hot water process begins to be used over 
these provinces ; . . . with it they can make indigo 
when the weather is too cold for the usual process 
of fermentation, and it gives --■ more beautiful 
and lighter indigo. ... A more complete and 
certain extraction of the basis of indigo is effected 
by subjecting the plant to the action of water 
heated to about 150°-160°F.' Bridges-Lee (Ix.) 
claims an advantage by the employment of hot 
water, and heats the contents of the steeping 
vat gradually either by direct fire or steam 
pipes. It is also well known that the Java 
planters who have employed the /. arrecta, 
for several years past have favoured a hot- 
water process, and although the exact details 
of their methods have not been disclosed, it 
is certain that sulphuric acid is also em- 
ployed in the manufacture. Perkin (Chem. 
Soc. Trans. 1907, 91, 436) refers to samples oi 
Java indigo prepared by three distinct methods, 
viz. ' the new process with hot water,' ' the new 
process with cold water,' and 'the old process 
in which no chemicals are used.' There can 
be no doubt that by these hot water processes 
the indican is very rapidly hydrolysed by the 
ferment, and that the indigo eventually pro- 
duced is of a superior quality. During this 
hot extraction it appears preferable, as far as 
possible, to exclude air from the vat by means of 
a cover, and the necessity in this case is easy to 
understand, because the evolution of carbon di- 
osde and other gases which act as a protection 
to the indoxyl during the ordinary process of 
fermentation, is greatly decreased when operat- 
ing in this manner (Roxburgh, l.e.). Rawson (2.c ), 
who refers to a patent No. 167, 1892, granted 
to A. Schulte in Hofe, for manufacturing indigo 
on these lines, and also to Henly's ' heating 



INDIGO. NATURAL. 



117 



proceaa of 1888,' carried out numerous experi- 
ments on this subject with the /. sumatrana. 
In order to economise fuel the indigo plant was, 
in the first instance, extracted by the accumula- 
tive method; but, contrary to Expectation, this 
did not give such good results as a simple ex- 
traction in ordinary vats fitted with perforated 
steam pipes. He finally concludes, however, 
that except in wet or cold weather the hot water 
system offers no advantage over ordinary 
steeping carried out under favourable conditions. 
The indjgo made by this method was, however, 
oit better quality (76-77 p.c.) than that made in 
the ordinary way (50-65 p.c.). In regard to 
extraction of the plant by means of boiling 
water, or extraction by steaming, Rawson con- 
siders that the cost would be prohibitive. 

When the fermented liquid is run off into 
the oxidising vat, the residual plant stiU con- 
tains a small quantity of indoxyl. The question 
of a second steeping in order to recover this is 
referred to by Roxburgh as early as about 1797 ; 
he considers that a considerable economy wpuld 
probably be effected thereby ; but Bawson's 
(2.C.) experiments in this direction gave an 
unsuccessful result. Thomas, Perkin, and 
Bloxam (l.c.) suggest that the employment of 
a slightly acid water for this purpose should be 
advantageous, and that the amount of indoxyl 
retained by the plant residue is probably 
greater than the 6 p.c. (on the total colouring 
matter) as believed by Rawson to be the case. 
The extracted plant, known as ' sect,' is a valuable 
manure. _ 

The oxidation vat. Although the oxidation 
of the fermented liquid was until very recently 
carried out to some extent by ' hand beating,' 
a method practised over a century ago, accord- 
ing to Bancroft (i!.c.),tliis operation is commonly 
effected by machinery. The apparatus is 
identical with, or very similar to the ' beating 
wheel,' a rimless wheel, the spokes of which 
are paddles, and which is now very generally 
employed in India. Geneste in 1888 patented 
the pumping in of air, and Bridges-Lee (2.c.) 
in 1891 a shower-bath arrangement, as improve- 
ments in the method of oxidation. Rawson 
again (1902, Eng. Pat. 173) proposed to treat 
the liquid with acid and an alkaline persulphate ; 
but although excellent results were obtained 
in the laboratory, these were not satisfactory 
on the manufacturing scale. As the outcome 
of an elaborate investigation, Rawson considers 
that the oxidation of the fermented liquid by 
blowers and compressors is superior to wheel 
beating, the yield being thereby increased about 
20 p.c. 

It has long been the custom to facilitate the 
deposition of the indigo by what were termed 
'preoipitants,' and experiments are recorded by 
Roxburgh, who employed for this purpose 
ammonia, stale urine, caustic lye, lime water, and 
potassium ferrocyanide. That such chemicals 
must be considered to have assisted in the more 
rapid oxidation of the indoxyl is certain, and 
their effect is not to be confused with the mere 
settlement of the indigo by the use of slaked 
lime, as adopted by the Chinese. 

In 1894 Coventry patented a process which 
was based on the employment of lime under 
certain conditions. The invention consisted in 
the employment of a special vat intermediate 



between the steeping and oxidising vats; in which 
the fermented liquor was treated with lime. A 
copious precipitate of calcium and magnesium 
carbonates was thus produced, which on settling 
carried down various impurities. The super- 
natant liquid was then oxidised in the usual 
manner. The indigo thus produced is somewhat ' 
contaminated with lime, and the removal of this 
is subsequently effected by the addition of a 
certain amount of acid to the ' mal ' in the 
boiler. Indigo prepared in this manner is of 
superior quality, and although not equal to the 
Java product resembles the latter in contain- 
ing some quantity of indirubin. According to 
Rawson a substantially increased yield of colour- 
ing matter is given by this process. 

Caustic soda added to indigo liquor before 
oxidising behaves very similariy to lime, and 
on the large scale gave an increase of 43 p.c. of 
dry indigo as weighed. Sodium peroxide also 
gave an average increase of 33 p.c, but on the 
whole was not so serviceable as caustic soda 
(Rawson). 

The oxidation of the fermented plant 
extract in the presence of ammonia, first 
mentioned by Roxburgh (J.c.), was patented by 
Micheain 1876, whereas Genestein 1889 suggested 
the use of caustic soda and ammonium sulphate 
instead of liquid ammonia itself. The use of 
ammonia is mentioned as beneficial by Geor- 
gievics (Z.C.), and there appears to be no doubt 
that it is superior to the other reagents which 
have been employed for this purpose. In its 
presence the indoxyl is rapidly oxidised to 
indigotin, and the precipitated colouring matter 
settles well. The more general employment of 
ammonia in India has resulted from the work of 
Rawson, and its use in conjunction with the 
steam injector blower constitutes the most 
important improvement which he has recom- 
mended to the notice of the indigo planters. 
The procedure adopted by Rawson consists 
briefly in Connecting the outlet of an ammonia 
still (containing lime and ammonium sulphate) 
loosely with the steam blower, so that when in 
action, ammonia, air, and steam are injected into 
the vat by means of perforated pipes laid at 
the bottom of the receptacle. During the 
operation the temperature rises" 10°-15°B'., and 
the oxidation is rapidly completed. The 
employment of ammonia gas and steam in con- 
nection with the beating wheel gives also 
satisfactory results. By these methods Rawson 
describes increases in the yields of dry indigo, 
varying from 37 to 63-8 p.c., and considers that 
the average increase of colouring matter is 
about 34 p.c. as compared with th&t given by 
the ordinary oxidising process. 

On the other hand, Bergtheil (Report of the 
Indigo Research Station, Sirsiah, 1906, 6) states 
that the ammonia process effects very little, if 
any, improvement over ordinary oxidising when 
this is carried out under optimum conditions of 
speed, weather, water, &c. 

After the indigo has settled in the vat, the 
supernatant liquid, or ' seet ' water, is run off as 
completely as possible. This seet water, as a 
rule, contains more or less colouring matter in 
suspension, and it is during this operation that 
a considerable loss of indigo occurs, which may 
reach as much as 20 p.c. (Rawson). This, as 
a rule, is much reduced by using an alkali in 



118 



INDIGOj NATURAL. 



oxidismg, on account of the readier settlement 
of the precipitate. Bawson found that filter 
pressing cannot be adopted in tlii& respect, but 
suggests treating the ' seet ' water with an alkali 
by which the suspended indigo more readily 
subsides. On the other hand, Eergtheil (1909) 
recommends the employment of ammino-ferric 
as an aid to the deposition of the indigo 
precipitate in the oxidation vat. 

Final treatment of indigo. According to 
Bancroft (l.c.) it was the practice of some manu- 
facturers in the East Lidies to purify their 
indigo by boiling it with water and fossil alkali 
(so(£i), whereas Boxburgh, as well as de Cosigny, 
recommended also the action of a diluted sul- 
phuric aoid. The more general practice, until 
very recently, in India has consisted in merely 
boiimg the semi-fluid indigo paste in a large 
cauldron, but the use of a dilute sulphuric acid 
appears now to be very generally adopted. 
According to Bawson the quality of the indigo 
may be in this way improved S-10 p.c. At the 
close of the operation the indigo is allowed to 
settle, the acid liquid run off, and the precipitate 
treated with fresh water and again boiled. 

The subsequent filtering, pressing, and 
drying operations call for no special comment. 
The Blow drying of the product appears to 
be most advantageous, and in this ' way an 
indigo of slightly higher percentage than when 
the mass is dried artificially is produced. This 
is accounted foi by the fact that certain 
impurities of the indigo in the presence of 
moisture undergo gradual decomposition with 
evolution of ammonia and other gases. 

Brigga (Fat. Spec. 292, 1906) has devised an 
apparatus for drying the indigo paste, and 
simultaneously converting it into powder. An 
iUustratiou of this machine, essentially a revolving 
drum, appears in Bergtheil's Beport, 1906, 12. 
Attempts, moreover, are being made to place 
natural indigo on the maiket in - the paste 
form (ibid. 1910). 

Constituents of Natural Indigo. 

In addition to indigotin natural indigo 
contains varying proportions of indirubin, 
indigo brown, indigo gluten, and mineral 
matter. Indigo yellow or keempferol is also 
present as a rule when the /. arrecta has been 
employed for the manufacture. • 

Indirubin. The identity of the natural 
indirubin or indigo red, with the artificial pro- 
duct prepared according to Baeyer's method {l.c.) 
about which there wasformerly some controversy, 
appears now to be fully established (Marchlewski 
and BadcMe, J. Soc. Chem. Ind. 1898, 17, 434). 
Bloxam at one time (Chem. Soc. Trans. 1905, 
87, 979) considered that a red substance other 
than indirubin was present in some quantity in 
natural indigo, whereas BergtheU (Beport of the 
indigo Besearch Station, Sirsiah, 1906) has 
stated that 'decisively there is more thaji one 
red body in most commercial indigos.' The 
investigation of numerous samples of the 
dyestul by Ferkin and Bloxam (Chem. Soc. 
Trans. 1907, 91, 279, and 1910, 97, 1461) 
indicate, however, that this is not the case. 
Whereas certain varieties of natural indigo, 
notably Java and Coventry process indigos, 
contain notable amounts of indirubin, it is 
probable that a trace occurs in all samples of 



the natural dyestuS. That the indirubin 
originates from the indican existing in the leaves 
of the various species of Indigofera, and is due 
to no second constituent of the plant, is now 
certain, and its production is to be explained in 
all cases as due to the condensation of isatin 
with indoxyl. Thus it has been shown by 
Thomas, Bloxam, and Ferkin (Lc.) that indigo 
containing indirubin can be readihrprodnced from 
indican by a repetition of the factory method, 
and again isatin itself has been isolated from 
natural indigo rich in indirubin (Ferkin, Chem. 
Soc. Proc. 1907, 23, 30). The formation of the 
isatin is favoured by special circumstances such 
as the oxidation of the indoxyl by air in the 
presence of alkali or acid, and may also be 
affected to some extent by temperature. That 
indoxyl can be converted into isatin without an 
intermediate formation of- indigotin has been 
shown by the Badische AnUin und Soda- 
Fabrik (D. B. F. 107719, 1898), and it has 
been ifound by Ferkin (Chem. Soc. Trans. 1909, 
85, 847) that indoxylic acid, on standing in the 
presence of moist air, is converted chiefly into 
indirubin, although some quantity of indigotin 
together with a substance, probably indigo 
brown, and traces of isatin are simultaneoudy 
produced. Again it has been pointed out 
(T. B. & F.) that the indican present in air- 
dried leaves of the indigo plant slowly disappears 
and, according to Ferkin (private communica- 
tion), this is accompanied in most cases by a 
development in the leaf of considerable quantities 
of indirubin. It appears probable that this so- 
called < secondary ' oxidation of the indoxyl 
proceeds according to the following scheme : 

CeH4<^^CH, -> CeH.<g°>CH-OH 



->C!.H,<^0>CO 



and may also be indirectly the cause of the 
production of indigo brown. The following 
are the results of analyses illustrating the 
percentages of indirubin and indigotin in certain 
indigos (B. and F.) : — 

Java Indigo. — New process with hA water. 

Total colour- 
Sample, ing matter. Indigotin. Indirubin. 

1. 75-20 67-76 7-43 

2. 73-60 63-86 9-61 
6. 62-91 67-35 501 

Java indigo. — New process with cold water. 
1. 72-88 69-23 3-06 

8. 71-02 66-35 4-04 

9. 58-30 55-61 2-15 
Java indigo. — Old process mthovt chemicals. 

13. 74-96 72-89 1-74 

15. 69-54 68-26 0-99 

Coventry. — Process indigo, 
61-76 56-63 6-23 

Finally, Bloxam and Ferkin refer to an 
abnormal sample of laboratory indigo prepared 
from pure indican, which contained 88-9 p.c. of 
colouring matter, and of tins 25-83 p.c. was indi- 
rubin. 

Though indirubin was at one time con- 
sidered to be a valuable constituent of natural 
indigo (cp. Bawson and Knecht, J. Soe. Dyers, 
1888, 4 ; Hummel, ibid. ; and BergtheU, 
Beport Indigo Besearch Station, Sirsiah, 1907, 
7) it is now known that such is not the case. 



INDIGO, NATURAL. 



119 



Fasal (Mitt. K. Tech. Gew-Mus. Wien. 1895, 
11, 307) found that the shade of colour given 
by an indirubin vat became bluer from day to 
day, and that this was due to the formation of 
indozyl by the further reduction of the leuco- 
indiiubin. More recently Perkin (Chem. Soo. 
Froo. 1909, 26, 127) has shown that in addition 
to indozyl oxindole is simultaneously produced, 
and this is in harmony with the formula 
assigned by Baeyer (I.e.) to this substance. 

NH-CO^ • ^-^^1'^ 

In vat dyeing, therefore, indirubin may 
produce not more than one-half its weight of 
indigotin. Matthews (J. Soc. Chem. Ind. 1902, 
21, 22), again, points out that indirubin requires 
for reduction a much stronger reagent than 
indigotin, and as a result the greater part of 
this dyestuS is not attacked, but settles to the 
bottom of the vat. 

On the other hand, indirubin disulphonio 
acid is, according to Fasal (2.C.), and also to 
Bawson and Enecht {l.c. ), a useful dyestufi, and 
gives colours much faster to light than sodium 
indigotin disulphonate, the 'indigo extract' of 
commerce. 

Indigo brown. An important impurity of 
natural indigo is the so-called indigo brown, a 
product isolated and cursorily examined by 
both Chevreul (Gmelin, Handbook of Chem. 1859, 
13, 48) and Berzelius {ibid.). In order to 
isolate this product, the latter chemist digested 
indigo with boiling dilute sulphuric acid to 
remove indigo gluten, and subsequently with 
potassium hydroxide to dissolve the brown. 
The alkaline liquid was neutralised with acetic 
acid, evaporated to dryness, the residue digested 
with- alcohol, and the solution evaporated. 
Thus obtained the indigo brown consisted of a 
dark-coloured resin, soluble in alkaline solutions. 
According to Schunck (Phil. Mag. 1855, [iv.] 10, 
74, and ibid. 1858, 15, 127) the indihumin 
Cj(,H,0,N produced in conjunction with other 
brown amorphous products by the action of 
dilute acids on his indican was, perhaps, identical 
with indigo brown. 

Perkin and Bloxam (Chem. Soc. Trans. 1907, 
91, 279) extracted Bengal indigo, which had 
been already digested with boiling dilute 
hydrochloric acid to remove the gluten, with 
boiling pyridine. In addition to a little indi- 
rubin the product contained three substances : (a) 
the main constituent, CijHjjOjNj (?) insoluble 
in alcohol and acetic acid, (6) C^tHjsOeN, (?) 
soluble in acetic acid, and (c) CieH,404Nj (?) 
soluble in alcohol. These compounds, the 
molecular weight of which is uncertain, consist 
of brown amorphous powders, closely resembling 
one another in gener^ property, and are readily 
reduced by zinc dust in alkaline solution with 
formation of pale brown liquids. When digested 
with boiling 50 p.o. potassium hydroxide solution 
they give some quantity of arUhranilie acid, a 
point which indicates that they are derived from 
indoxyL At the same time a brown resinous 
substance is also produced, and this studied in 
the case of the main constituent. (a) CigHi^OgNg 
contained 0=71-39; H=405; N=7-94. 
Natural indigo further contains a small quantity 
of a brown substance (o), insoluble in pyridine, 
but soluble in boiling dilute alkali (Chem. Soc. 



Trans. 1910, 97, 1473), and is distinguished from 
the substances above enumerated by the fact 
that it is not susceptible to sulphonation (with 
96 per cent, sulphuric acid) or conversion by 
this means into a product soluble in water. 
In the analytical method described by Bawson 
(J. Soo. Chem. Ind. 1899, 18, 251) this brown 
material, at least in part, consists of the impurity 
which is carried down by a precipitation of 
barium sulphate in the liquid. There is now 
considerable evidence in favour of the view that 
the constituents of indigo brown are derived 
from indoxyl during the manufacture of indigo 
from the plant. The fact that indican itself, 
when boiled with dilute acids, produces the very 
similar indoxyl brown, and the isolation of 
brown substances, although in trifling amount, 
from indigo prepared by the hydrolysis of pure 
indican in the laboratory, harmonises with this 
suggestion. 

Beyerinck (Proc. Hoy. Akad. Scien. Amster- 
dam, 1899, 120) observed that the disappearance 
of indoxyl in a dying woad {Isatia tinctoria) leaf 
is accompanied by the appearance of brown 
substances. Again, he states that < strong acids, 
just as alkalis . . . favour'the formation of indigo 
from indoxyl, but then part of this substance 
constantly changes into a brownish-black 
matter.' It has also been noted by Thomas, 
Perkin, and Bloxam that the disappearance of 
indican in the leaves of the /. sumatrana on 
keeping is accompanied by the formation of 
brown extractive matter. Eawson, again (Report 
on the Cultivation and Manufacture of Indigo, 
Mozzufferpore, 1904), says, ' The blower ... by 
quickly getting rid of COj gas , . . prevents de- 
composition of a portion of the colouring matter 
into worthless brown substances, which takes 
place to a greater extent under other condi- 
tions.' All indigos, moreover, appear to contain 
indigo brown so that this property is irrespective 
of their origin, which may have been due to 
such distinct plants as the Indigoferce, the Poly- 
gonum iinctorium, or the LoncJiocarpua cyanes- 
cens of West Africa. Finally, it has been shown 
by. Perkin (I.e.) that among the decomposition 
products of commercial indoxylio acid which 
has been kept for a long time, a brown compound 
exists, which has a very similar percentage 
composition, and is probably identical with the 
main constituent of indigo brown. It is quite 
possible that indoxylic acid is produced during the 
fermentation process (Perkin). The percentage 
of indigo brown, soluble in pyridine in natural 
indigos is very variable, and appears to depend 
upon the details of manufacture. Analyses 
made by Bloxam and Perkin (Chem. Soc. Trans. 
1910, 97, 1472) gave the following result : — 

Jam indigo, Java indigo, Java indigo, Coventry N-ae 
mw -process, new -process, otdina/ry process Bengal 
hot water, cold w(Uer. process. indigo, indigo. 
6-4 6-2 4-15 8-7 960 

Except in the case of the Coventry process 
indigo, these samples had all been derived from 
the /. arreda. The average amount of crude 
indigo brown — containing, however, some mineral 
matter — ^in numerous samples of Bengal indigo 
was 14 p.c. (Chem. Soo. Trans. 1907, 297). 

Indigo brown dissolved in alkaline^ hydro- 
sulphite solution does not colour fabrics, and 
appears to be entirely devoid of tinctorial 
property. The frequently asserted superiority of 



120 



INDIGO, NATURAL. 



the natural over the artificial variety of indigo 
cannot therefore be accounted for in this 
manner. 

Indigo gluten. Indigo gluten was first 
isolated from crude indigo by Berzelius (Berz. 
Jahresb. 7, 26), who extracted it with dilute acid, 
neutralised the extract with chalk, evaporated 
to drjmess and dissolved out the gluten with 
alcohol. It was subsequently prepared by 
Orchardson, Wood, and Bloxam (J. Soo. Chem. 
Ind. 1907, 26, 4), who describe it as a horny 
mass, which on grinding gives a light biscuit- 
coloured powder, and when heated evolves 
ammonia. In cake indigo it appears to exist in 
combination with mineral matter, possibly as 
a calcium compound, for though itself readily 
soluble in water it can only be removed from the 
dyestufi by means of dilute mineral acid. A 
considerable quantity of this substance is 
frequently present in indigo, and Perkin and 
Bloxam (I.e.) found that when the crude Bengal 
variety containing approximately 62 p.o. of 
indigotin was digested with dilute hydrochloric 
acid, it lost 21 -6 p.o. of its weight. This figure 
naturally includes some quantity of mineral 
matter simultaneously removed by the acid. It 
has been suggested that this compound plays 
an important r61e in the dyeing operation, and 
accounts in part for the alleged superiority of 
natural over artificial indigo. This point, 
however, has not been scientifically investi- 
gated. 

Indigo yellow. The first application of the 
term ' indigo yellow ' to a substance existing in 
natural in£gos is due to Bolley and Crinsoz 
(J. 1866, 673), who state that it is to be 
found in the Bengal variety, and can be isolated 
by sublimation. It is described as golden-yellow 
needles, sublimiiig at 130°, and soluble in soda 
lye. Cnide Bengal indigo, however, gives no 
sublimate of this character (Perkin, Chem. Soo. 
Proc. 1906, 22, 198), but by submitting refined 
indigo, or the commercial synthetical variety to 
sublimation with limited access of air, a trace 
of a yellow compound CisHjOjNj is produced. 
This substance, however, is insoluble in alkaline 
solutions, and cannot, therefore, be the indigo 
yellow of Bolley and Crinsoz, 

Bawson (J. Soc. Chem. Ind. 1899, 18, 251) 
detected in Java indigos a yellow compound, 
present usually to the extent of 2-3 p.c., although 
in one special sample as much as about 20 p.c. 
occurred. This substance was soluble in alkalis 
with a yellow colour ; on heating it partially 
sublimed, and had tbe properties of an adjective 
yellow dyestufiE. A more recent investigation 
(Perkin, Chem. Soc. Proc. 1904, 20, 172) has 
indicated that this in reality is kcempferol 



OHi 



/\/^ 



OH 



COH 



^^co/' 

a trihydroxy flavonol known to exist (Chem. 
Soc. Trans. 1902, 81, 587) in the flowers of the 
Ddphinium consolida (Linn.) and other plants. 
Ultimately it was shown that the leaves of the 
/. arrecta, from which Java indigo is pre- 
pared, contain sometimes as much as 4 p.c. of 
a glucoside kcempferitrin C),H,gOii, almost 
colourless needles, m.p. 201°-203°, which 



when digested with acid gives ksmpferol and 
rhamnose 

C2,H3„0,4+-4HjO=Ci6HioO.-f2CeH,,Oj,H,0. 
This compound is not hydrolysed by the 
indigo enzyme, and no enzyme has as yet been 
isolated from the plant possessing such a pro- 
perty. It is likely (Chem. Soo. Trans. 1907, 91, 
435) that the use of sulphuric acid, when manu- 
facturing Java indigo, may result in the con- 
tamination of the dyestufi with ksempferol. 
When the wet indigo sludge or ' mal ' is boiled in 
the ' mal ' boiler with addition of a little of the 
acid, the kaempferitrin present in the adhering 
water will be hydrolysed, and the insoluble 
colouring matter remain with the indigo. 
Samples of Java indigo more recently obtained 
contained only a trace (0-2 p.c. approx.) of 
kaempferol, whereas in a sample of the new 
Bengal indigo manufactured from the /. arreda 
approximately the same quantity was detected 
(Perkin, private communication). If indigo 
mixed with kasmpferol is cautiously sublimed 
the sublimate then contains appreciable quan- 
tities of this yellow colouring matter, and it 
seems likely, therefore, that this is in reality 
the indigo yellow of Bolley and Crinsoz, but 
that the indigo experimented with by these 
authors did not, as they supposed, originate 
from Bengal. The leaves of the /. sumatrana, 
tbe Indian indigo plant, contain but the merest 
trace of a yeUow dyestufi resembling ksempferol, 
but according to Henry fGmelin's Handbook of 
Chem. 1846, 13, 50) the Polygonum tinotorium, oi 
Chinese indigo plant, contains appreciable 
quantities of a yellow colouring matter. 

The AiTAiiYSis of Inoigo. 

The methods which have been proposed foi 
the analysis of indigo are of a varied character, 
and the literature upon the subject is extremely 
voluminous. 

These may be classified as follows : methods 
(o) involving the extraction of impurities with 
volatile solvents (Schutzenberger, Die Farb- 
stofie, ii. 526) ; (b) the extraction of indigotin 
with coal tar oil (Stein, Die Priifing der Zeug- 
farben) ; with aniline (Honig, Zeitsch. angew. 
Chem. 1899, 280) ; with phenol (Brandt, J. Soc. 
Dyers. 1898, 34) ; with naphthalene (Schneider, 
ibid. 1895, 194); with nitrobenzene (Gerland, 
J. Soc. Chem. Ind. 1897, 108); with aceto-sul- 
phuric acid (Mohlau and Zimmermann, Zeitsch. 
farb. text. Chem; 1903, 10, 189) ; (c) the extrac- 
tion of indigotin by sublimation (Lee, Chem. 
News, 1884) ; (d) the extraction of indigotin by 
processes of reduction, lime, and ferrous sulphate 
(Berzelius), stannous chloride and caustic soda 
(Dana, Jahres. f. prakt. Chem. 26, 398), zinc and 
caustic soda (Owen, J. Amer. Chem. Soo. 10, 
178), grape sugar, alcohol, and alkali (Fritzsche, 
Dingl. poly. J. 1842, 86, 306), and hydrosulphite 
and lime (Bawson, I.e.) ; (e) estimation of 
nitrogen (Voeller, Zeitsch. angew. Chem. 1891, 
110). 

More important, however, are the methods 
based upon the titration of a solution of the 
su]phona.ted indigo by oxidising agents (/) 
chlorine water (Berzdius), chloride of lime 
(Chevreul, Lecons. d. chem. appUq. de la teinture, 
ii.), potassium chlorate and hydrochlorio acid 
(Bolley, DingL poly. J. 119, 114), potassium 
dichromate and hydrochloric acid (J. pr. Chem. 



INDIGO, NATURAL. 



121 



1851, 18, and Sohlumberger, Bull, de la Soc. 
MuUhouse, 1863, 210, 284) potassium dichiomate 
and oxalic acid (Kinloy, Chem. News, 1863, 210, 
284), potassium feiricyanide (Ullgren, Annalen, 
136, 96), and potassium permanganate (Mohr, 
Diugl. poly. J. 132, 363), and by reducing 
agents, (g) sodium hydrosulphite (Miiller, Ber. 
1880, 13, 2283), and titanous chloride (Knecht, 
J. Soc. Dyeis. 1904, 97, and ibid. 1905, 292). 

Finally {h) colorimetric methods (DingL poly. 
J. 27, 64, and 40, 448) ; (t) spectrum analysis 
(Wollf, Zeitsoh. anal. Chem. 17, 65, and ibid. 23, 
92) ; and (k) dye trial methods (Chevieul, 2.C., and 
Grossmann, J. Soc. Dyers. 1897, 124) have been 



Qf these methods of indigo analysis, modificac 
tions of Mohr's permanganate process are most 
generally employed, although others involving the 
reduction of sulphonated indigo with titanous 
chloride and sodium hydrosulphite are to some 
extent in vogue. 

The permanganate methods. In order to 
eliminate the error due to the oxidising action 
of permanganate upon substances other than 
indigotin which are present in natural indigo, 
Bawson, who has been the pioneer in this 
respect, has devised two processes. 

Salting out method. 0-5 gram of finely 
powdered indigo mixed with its own weight of 
ground glass is sulphonaied in a porcelain 
crucible by means of 20 c.o. of concentrated 
sulphuric acid at 70° for f-1 hour; the product 
is diluted with water to 600 c.c, and the liquid 
filtered to remove insoluble impurities. 60 c.c. 
of this solution are mixed with 60 c.c. of water 
and 32 grams of common salt, and after standing 
for 1 hour the precipitated sodium indigotin 
sulphonate is collected and freed from certain 
soluble impurities by washing with about 60 c.c. 
of salt solution (sp.gr. 1'2). The precipitate is 
dissolved in hot water, treated with 1 c.c. of 
sulphuric acid, diluted to 300 c.c, and titrated 
with a solution of N/50 potassium permanga- 
nate. The liquid gradually takes a greenish tint, 
and the final disappearance of this constitutes 
the end point of the reaction. According to 
Rawson, 1 c.c. of the N/50 permanganate corre- 
sponds to 0'0015 of pure indigotin (J. Soc. Dyers., 
1885, 74 and 201 ; A Manual of Dyeing, Knecht, 
Rawson, and Lowenthal, 1910, 817). 

Baiium chloride precipitation process. 0-5 
gram of indigo is sulphonated as before, and after 
diluting with water, but before making up to 
500 c.c, 10 c.o. of a 20 p.c solution of barium 
chloride are added. The barium sulphate 
formed carries down with it the suspended 
impurities of the indigo,^and the clear liquid can 
be pipetted ofi and titrated as before. The 
results are practically identical with those given 
by the ' salting out ' method (Rawson, J. Soc. 
Chem. Ind. 1899. 251). 

Bloxam {ibid. 1906, 735) notes that the barium 
precipitate thus produced is always coloured 
blue, and this is confirmed by Bergtheil and 
Briggs (ibid. 1906, 729). The latter authors 
contend that the results given by this modifica- 
tion of Rawson, are therefore too low, and con- 
sider that this defect is obviated by adding 
instead of barium chloride freshly precipitated 
barium sulphate to the indigo mixture. 

Grossmann {■Ond. 1905, 308) throws down the 
impurities from the indigo solution with calcium 



carbonate. Bergtheil and Briggs (I.e. ), and also 
Bloxam (2.C.). £md that some quantity of the 
colouring matter is also precipitated in this 
way. Knecht, however, recommends its success- 
ful use even in larger quantity (J. Soc. Dyers. 
1904, 97, and 1905, 292) in connection with his 
titanous chloride method; but Bloxam (i.e.) 
points out that such being the case this can 
only be due to the observance of conditions 
which are not stated in Knecht's paper. 

Hydrosulphite method. This process, devised 
by MuHer (Ber. 1880, 13, 2283), depe^ds upon the 
fact that sodium hydrosulphite (NajSjO,) 
quantitatively reduces pure indigotin sulphonic 
acids to their corresponding leuco compounds. 
The solution of the hydrosulphite contained 
in a stone bottle, is covered with a layer of 
petroleum to prevent oxidation and connected 
with a supply of hydrogen gas. By means of a 
siphon, or other convenient arrangement, the 
liquid can be drawn into a burette. The solu- 
tion should be equivalent to about 1 c.c. =0-0025 
gram of indigotin, and the titrations are 
performed in an atmosphere of hydrogen or 
coal gas. 

Titanous chloride method. This reagent is 
much more stable than sodium hydrosulphite, 
and Knecht (J. Soc. Dyers. 1904, 97, and 1905, 
292) was the first to recommend its use for the 
analysis of indigo. The apparatus employed is 
similar in character to that required for the 
hydrosulphite 'process, and the titration is 
carried out in an atmosphere of carbon dioxide. 
If the. reduction of the indigotin is effected 
by the titanium chloride in the presence of 
mineral acid, no definite end-point can be 
observed (Knecht), but by the addition of salts 
of tartaric acid this end-point is rendered quite 
definite. 

In working with natural indigo, Knecht 
(Manual of Dyeing; Knecht, Bawson, and 
Lowenthal, 822) sulphonates 1 gram of indigo 
with 5 c.c of 100 p.c. sulphuric acid at 90° for 
1 hour. The solution diluted to 300 c.c. is 
warmed and slowly treated with 12 grams of 
chalk, cooled, made up to 600 c.c, and 60 cc. 
of the clear liquid to which 25 c.c. of a 20 p,c., 
solution of RocheUe salt has been added, is 
titrated whilst boiling with titanium chloride. 

On account of thesparing solubility of RocheUe 
salt, Bloxam (I.e.) recommends the use of 
sodium tartrate, but states that the presence of 
excess of this or of RocheUe salt (as advocated by 
Knecht) is to be avoided, or otherwise too high 
percentages of indigotin are indicated. In the 
case of pure indigotin (1 gram) sulphonated 
with 20 c.o. of 100 p.c. sulphuric acid, and made 
up to 500 c.c. with water, 25 c.c. of this liquid 
(containing 1 c.o. of acid) requires 4 grams of 
the sodium tartrate to give quantitative results 
when titrated with a solution of titanium 
chloride containing 1 cc. of concentrated hydro- 
chloric acid per 60 c.c of solution. 

Bloxam (Chem. Soc Trans. 1906, 87, 975 ; 
J. Soc Chem. Ind. 1906, 25, 735), Orchardson, 
Wood, and Bloxam (ibid. 1907, 26, 4), and 
Gaunt, Thomas, and Bloxam (ibid. 1907, 26, 
1174), have critically investigated the subject 
of indigo analysis. Among the methods foi 
preparation of pure indigotin, that involving the 
crystallisation of crude material from nitro- 
benzene was discarded as untrustworthy, but the 



122 



INDIGO, NATURAL. 



elaborate process of the B. A. S. F. Co. (Biochuie, 
1900) was found to give a pure substance. On 
the other hand, sublimation under reduced pres- 
sure in Jena flasks immersed in fusible metal at 
370°-390°, gave, with synthetical indigo of 92 p.c. 
(approx.), a beautifully crystalline substance, 
which, after washing with boiling acetic acid, 
followed by boiling alcohol, was usually chemi- 
cally pure. The permanganate factor resulting 
from experiments with these specially purified 
materials was 1 c.c. of permanganate solution 
1/1000=000222 gram indigotin solution 1/6000, 
and is in agreement with that previously adopted 
by the B. A. S. F. Co., but differs considerably 
from that employed by Rawson (1 c.c. of N/5Q 
permanganate =0 '0016 indigotin) (Z.c). Wan- 
gerin and Vorlander (Zeitsoh. Farben und 
Textilchemie, 1902, 1, 281) have stated that 
indigotin suffers loss of strength by oxidation, 
even when it is sulphonated by 94 p.c. sulphuric 
acid at 95°-100° for half an hour, whereas acid 
of 8 p.c. fuming acid gives a deterioration of from 
2 to 14-2 p.c, according to the time of heating. 
With the indigotin, however, purified as above, 
Bloxam showed that heating with 20 p.c. fuming 
acid for | of an hour at 97° gave no loss, whereas 
with 30 p.c. acid for 20 minutes at 97° a deferio- 
ration of only 1 p.c. could be observed. In both 
these cases indigotin tetrasulphonio acid was 
produced. 

The tetrasulphbnate method. As a result of 
these experiments a method for the analysis of 
indigo based on sulphonation with.fuming acid 
was devised. 1 gram of the indigo, and .2-3 
grams of purified sand (powdered glass contains 
iron, and should not be employed), is treated 
with 6 c.c. of 26 p.c. fuming sulphuric acid 
tor half an hour in the water oven, and the 
solution is made up to 600 c.c. with water. 
100 cc. of this solution is treated with 100 c.c. 
of potassium acetate solution (460 grams per 
litre) which causes the precipitation of indigotin 
tetrasulphonate. The mixture is now warmed, 
and on cooling finally in ice-water, the salt 
completely separates in a crystalhne condition. 
This is collected by means of the pump on a 
Grooch crucible, and washed free from the 
brown supernatant liquid with a solution contain- 
ing 90 grams of potassium acetate and 5 cc. 
of acetic acid in 600 cc of water. The product 
is dissolved in 200 c.c. of water, and 20 cc. of 
this solution, diluted with. 80 c.c. of water, is 
treated with 0-6 cc. of sulphuric acid, and 
titrated with permanganate (1/1000). In order 
to verify the accuracy of this method, 
Orchardson, Wood, and Bloxam studied the 
behavionr of indigo brown and indigo gluten, the 
main imparities of indigo, when submitted to 
the analytical process, as this subject had not 
been investigated by previous workers. Indigo 
brown, when sulphonated with 96 p.c. acid gives, 
when dissolved in water, a dark-brown liquid, 
which is attacked by permanganate, though not 
perhaps so readily as the indigotin sulphonic 
acids, whereas indigo gluten gives similarly a b'ght 
yellow solution, which is very rapidly oxidised 
by the reagent. On the other hand, ksempferol 
or indigo yellow, treated in the same manner, 
gave a product which most readily absorbs per- 
manganate, and, indeed, Rawson (J. Soc Chem. 
Ind. 1899, 261) had already pointed out its 
deleterious effect in indigo analyses. Finally, 



these authorsprepared and submitted to analysis 
by Bloxam's process mixtures containing known 
quantities of indigotin and one or other of all of 
these impurities, with the result that the colour- 
ing matter was thus estimated with considerable 
exactness. Bloxam (Chem. Soc. Trans. 1910, 
97, 1473), by an adaptation of the pyridine 
method for the estimation of indirubin (l.e.), in 
which the impurities are eliminated by a process 
of extraction, has analysed natural indigos, and 
obtained the same figures as those given by the 
tetrasulphonate method. Again, by Knecht's 
titanium chloride method, and employing the' 
modifications above described, this process can 
also be effectively worked. It is only reasonable 
to suppose that an analysis based on the selective 
precipitation of the sulphonated colouring matter 
is more likely to be efScient, than that wMch pre- 
sumes the deposition of varied impurities of a 
diverse chemical character by one specific reagent, 
and the somewhat lower results given by the 
tetrasulphonate method, as distinguished from 
those yielded by the processes previously in use, 
are in' reality due to the almost complete elimina- 
tion of these impurities from the indigotin 
sulphonic acid during the analysis. Rawson 
(2.C.) is, however, of opinion that the effect 
of these impurities on the analytical results 
has been much overrated; "but, on the othei 
hand, no experimental evidence is given in 
support of this view (Manual of Dyeing, l.c. ,. 
818). 

The action of potassium permanganate on 
solutions of the indigotin sulphonic acids is of 
interest, because the amount of the reagent 
necessary for the decolorisation of the liquid 
varies to some extent with the concentration 
(Rawson, A Dictionary of Dyes, Mordants, &c., 
by Rawson, Gardner, and Laycock, 1901, 187). 
At the concentrations employed by the B. A. S. F. 
Co., and adopted by Bloxam {I.e.), 1 gram of 
indigotin as sulphonic acid requires 0'46 gram 
of permanganate for decolorisation, whereas 
the equation 

50i,H,„OaNa-f4KMnOi+6HjSO, 

=I0C8H5OjN+2KjSOi-|-4MnSO4-l-6H,0 

implies that 0-4824 gram of the reagent is 
necessary. Again, for the Oxidation under 
similar conditions -of indirubin sulphonic acid 
considerably less permanganate is required, 
although the oxidation in this case is of a slower 
character. Bloxam and Ferkin (J. Chem. Socs^ 
1910, 97, 1462) consider, therefore, that the 
oxidation is of a complex nature, and consists 
either (a) of two distinct stages in the formation 
of isatin sulphonic acid, or (b) of two distinct 
reactions involving the production of two separate 
substances. According to the first suggestion 
the isatin formation from indigotin would be 
preceded by that of an intermediate compound 
(I.), whereas by the latter, in addition to isatin, 
a dehydroindigotin sulphonic acid (II.) is 
produced. 

II. C.H<cO>07.C^cO>0.H4. 

In case the first product of the reaction con- 
sists entirely of dehydroindigotin sulphonic acid ; 
this must, prior to further oxidation to isatin, 



INDIGO, NATURAL. 



123 



tako up two molecules of water with foTmation 
of dihydcoxy-indigotin (III.)- 

C.H4<C0>C(0H)C(0H)<^0^C.H.. 

In regard to the very small amount of 
permanganate required for the decolorisation 
of the indirubin sulphonio acid a similar explana- 
tion can be adopted. 

The Estimatiok of Indigos rich in iNDiEUBm. 

It is well known that indirubin is more 
resistant to oxidation and reduction than indi- 
gbtin, properties which also apply to the sul- 
phonio acids of these colouring matters. When 
dealing, therefore, with mixtures of these 
substances and employing either potassium 
permanganate, titanium chloride, or sodium 
hydrosiUphite, the indigotin is to some extent 
preferentially attacked, so that towards the end 
of the operation the colouring matter consists 
entirely of indirubin sulphonic acid. In the 
case of the former reagent, however, Koppeschaar 
(Zeitsch. anal. Chem. 1S99, 38, 1) finds that it 
is not possible to obtain trustworthy analytical 
figures with indigos in which some quantity of 
indirubin is present, although Bawson (l.c.) con- 
siders that the indirubin may be approximately 
estimated in this manner. Bloxam and Ferkin 
(CSiem. Soc. Trans. 1910, 97, 1462), however, 
support the view of Koppeschaar. The latter 
authors, who also experimented with titanous 
chloride, show that this reagent behaves in an 
identical manner towards both indigotin and in- 
dirubin sulphonic acids, but although the former 
is somewhat preferentially attacked, it is not 
possible in this way to differentiate as to the 
amount of each of the sulphonated colouring 
matters which may be present in a mixture of 
the two. On the other hand, according to 
Knecht, Bawson, and Lowenthal (A Manual of 
Dyeing, 821) indirubin present in mixtures of 
the two colouring matters may be approximately 
estimated by the hydrosulphite method. 

For analysis of indigos rich in indirubin, 
processes of extraction based on the greater 
solubility of the latter, have been usually em- 
ployed. 

Extraction with ether (Bawson, l.c.). From 
0-1 to 0-25 gram of the sample is boiled with 
about 160 c.c. of ether for half an hour. When 
cold the solution is made up to 200 c.c. with 
ether, mixed with 10 c.c. of water and well 
shaken. The suspended particles of indigotin 
settle immediately, and a clear solution of 
indirubin is obtained. A measured quantity of 
the solution is withdrawn, and compared in a 
colorimeter with a standard solution of indi- 
rubin. 

Extraction with acetic acid (Koppeschaar, l.c.). 
The indigo is extracted with glacial acetic acid, 
and the solution, which contains a mixture of 
indirubin and indigo brown, is treated with 
caustic soda. The indirubin, which is thus 
precipitated, is collected, redissolved in acetic 
acid, and estimated by comparison with a 
standard solution of the pure colouring matter. 

Extraction with acetone (Gardner and 
Denton, J. Soc. Dyers. 1901, 170). 0-2 gram of 
the indigo is digested for half an hour with 
100 c.c. of boiling acetone. After cooling the 
solution is made up to 100 c.c, with acetone, and 



then to 200 c.c. with 10 p.c. salt solution, and 
well shaken. The precipitate of indigotin, 
indigo brown, and other impurities, is removed 
by filtration, and the indirubin solution estimated 
colorimetrically with a standard solution of 
indirubin prepared with acetone and salt solu- 
tion in a similar way. 

Extraction with pyridine. Bloxam and 
Perkin (Chem. Soc. Trans. 1900, 97, 1460) find, 
as the result of experiments on mixtures of 
indigotin and indirubin, that neither com- 
mercial ether nor acetone are reliable solvents 
for the complete extraction of indirubin, and 
that their action, especially in the former case, 
is chiefly due to the presence of alcohol. Whereas 
acetic acid is efficient 'in this respect, and 
Koppeschaar's process gives approximately,good 
results, pyridine is a much better solvent, and 
a method for the complete analysis of indigos 
containing indirubin based on the application of 
this liquid is described by these authors. 

The indigo (0-25-1 gram) evenly incorporated 
with purified sand (20-30 grams) is introduced 
into a thin-waUed glass tube, termed the ' con- 
tainer,' closed at one end by means of cotton 
cloth, on which has been placed a layer of 
asbestos and sand or of sand alone. Sufficient 
sand is then added to form a layer on the 
surface of the indigo mixture, which is then 
covered with asbestos, and the container is 
now placed in a Soxhlet tube and extracted 
with boiling pyridine. The extract is distilled 
down to a small bulk, the residue treated with 
boiling water and again distilled, and this 
operation is repeated until the last traces of 
pyridine have disappeared. The precipitate, 
which consists of indirubin together with a little 
indigotin and indigo brown, is collected, freed 
from the latter by means of dilute alkali, and 
the residue is sulphonated with 5 c.c. of sulphuric 
acid at 100°. The product is dissolved in water, 
filtered, and the amounts of indigotin and 
indirubin present ascertained by means of the 
Duboscq tintometer. 

The residue in the containei is percolated* 
with water, followed with boiling dilute hydro- 
chloric acid to remove indigo gluten, and is 
now introduced into a beaker and dried. The 
colouring matter present is sulphonated with 
20 0.0. of sulphuric acid in the usual way, the 
product after dilution is filtered, and the 
solution of the indigo sulphonic acid is estimated 
with permanganate, employing the directions 
given by Bloxam {I.e.). Analyses of mixtures of 
pure indigotin and indirubin, and also of com- 
mercial indigos are given in the paper, and it is 
also pointed out that by this method an approxi- 
mate estimation of the indigo brown present in 
the latter can be carried out. 

The Esiimatioh of Indican m the Leaves 
OF Indigo Plants. 
Although someindication of the indigo-yielding 
capacity of the plant can be obtained by ordinary 
steeping experiments, this method was found by 
Bawson (Cultivation and Manufacture of Indigo, 
l.c.) to possess several drawbacks, and numerous 
experiments were therefore carried out by him 
on the quantitative formation of indigo from 
the leaf extract by -the simultaneous action 
of acids and oxidising agents. As regards the 
latter, ferric chloride, potassium chlorate, and 



124 



INDIGO. NATURAL. 



hydrogen peroxide were tried, but persulphurio 
acid gave much the best results. 

Persulphate method. 20 grams of leaves are 
extracted for 2 minutes with 250 c.c. of boiling 
water, the solution is strained through muslin, 
and the residues squeezed and washed with 
boiling water. The solution is treated with 
5 c.c. of 20 p.c. hydrochloric acid, and 40 c.c. 
of a 6 p.c. solution of ammonium persulphate. 
The persulphate is not added all at once ; at 
first 2 c.c. are added, after half an hour 2 c.c. 
more, and again 2 c.c. after another half an 
hour. After 2 hours the remainder of the 
ammonium persulphate is added, and when the 
mixture has stood foj: a further period of an 
hour, the indigo is collected and estimated by 
permanganate in the usual manner. Bergtheil 
and Briggs (J. Soo. Chem. Ind. 1906, 734) 
point out, however, that this process of Rawson's 
requires modification, as the addition of the 
reSigents at such a high temperature involves a 
loss of indigotin. The main features of a modi- 
fication of the process devised by these latter 
authors are the addition of acid to the cooled 
extract, and a determination of the course of the 
reaction, afteA* addition of small amounts of per- 
sulphate, by filtration of a portion of the mixture 
and the addition to the filtrate of a trace of 
the oxidising agent. 

Orchardson, Wood, and Bloxam {ibid. 1907, 
40 ; cp. also Bloxam and Leake, Research 
Work on Indigo, Dalsingh, Serai, 1905), who 
employ sulphuric acid and persulphate, arrived 
independently at the same conclusion. To 
200 o.c. of the leaf extracts these authors add 
100 c.c. of a mixture of equal parts of 2 p.c. 
ammonium persulphate, and 4 p.c. - sulphuric 
acid, and the mixture is kept at 60° for 1 
hour. ^ comparison of their methods with 
that of Bergtheil and Briggs indicated an 
identical result in each case, and an increase of 
20-25 p.c. of pure colouring matter in comparison 
with that yielded by Rawson's original process. 

The isatin method. Beyerinck (Froo. K. 
• Akad. Wetensch. 1899, 120), in discussing 
indican, suggested the possibility that by warm- 
ing its solution with isatin a quantitative yield 
of indirubin might be produced. Orchardson, 
Wood, and Bloxam (2.c.) have employed this 
reaction for the estimation of the leaf, and have 
devised the following method for this purpose. 

250 c.9. of extract, equivalent to 6 grams of 
the leaf, is treated with 0-1 gram of isatin, and 
the mixture boiled for 6 minutes to expel air, 
carbon dioxide being passed through the flask. 
20 c.c. of hydrochloric acid is then added by 
means of a tap funnel, and the whole kept boiUng 
for 30 minutes. The precipitate is collected on a 
tared filter, washed with hot 1 p.c. soda to 
remove brown compounds, then with 4 p.c. 
acetic acid and dried. An aliquot portion of the 
crystalline product is sulphonated, and analysed 
by the titanous chloride method, adopting the 
modifications employed by. Bloxam (I.e.). The 
indirubin thus obtained is usually almost pure 
(98-5 p.c), so that for an approximate estima- 
tion, the latter part of the process is unnecessary. 
Gaunt, Thomas, and Bloxam (ibid. 1907, 26, 66) 
have examined the process in greater detail, and 
point out that by its employment pure indican 
gives quantitative figures (cp. also Perkin and 
Bloxam, Chem. Soc. Trans. 1907, 91, 90). On 



the other hand, this method gives considerably 
higher figures, both with pure indican (16 p.c.) 
and the leaf extract (26 p.c.), than those which 
are obtained by the persulphate process (Orchard- 
son, Wood and Bloxam ; and Gaunt, Thomas, 
and Bloxam, I.e.). The unsatisfactory figures in 
the latter cases arise from a further oxidation 
of the indigo by the persulphate. That this 
isatin method does not appear to be affected 
by other plant constituents was shown by the 
successful estimation of indican, purposely added 
to an extract of the leaves of the Tephrosia 
purpurea (Pers.), a plant in which this glucoside 
is absent. 

Efpicibncy op the Process. 

The actual yield of indigotin from the plant 
during the manufacture is not discussed by 
Rawson (2.c.), but this author considers that if 
the suggestions enumerated in his report are 
adopted, there is little or no room for a remunera- 
tive alteration of the process. Bergtheil, on the 
other hand, considers that under the conditions 
he describes (1906, 12) the efficiency is repre- 
sented by an 82 p.c. yield, or that if to this 
be added the 6 p.o. DeUeved by Rawson to 
be retained by the extracted plant, 87 p.c. is 
thus accounted for. The quantity of indigo^ 
estimated refers to the precipitate present in 
the vat after oxidation, and from this must 
be, therefore, deducted the indigo (10-20 p.c.) 
lost by the ' running off ' of the ' seet ' water, so 
that the actual yidd of dry colouring matter 
will thus represent from 62 to 72 p.c. of the 
theoretical quantity. Recent experiments, how- 
ever, indicate that by adding aluminoferrio to 
the oxidation a more perfect settlement of the 
indigo is to be anticipated {ibid. 1909). 

Bloxam (Dalsingh Serai Report, and J. Soc. 
Chem. Ind. 1906, 26, 736), who examined the 
daily output of indigo (as pressed cake) fi:om the 
Fembarandah factory, found that the first 
cuttings of the plant (Moorhun mahai) repre- 
sented an approximate value of p-I495 p.c. of 
indigotin from the plant, whereas the second 
cuttings gave a value of but 0-1526. Assigning 
to the plant the low value of 0-3 p.c., a consider- 
able and serious loss is thus apparent. Moreover, 
the estimation of the results given by the 
' isatin ' method of leaf estimation, and of the 
finished cake by the ' tetrasulphonate ' process 
(I.e.), both of which have been stan(^rdised 
with extreme care, point to a loss during the 
manufacture much greater than has hitherto 
been acknowledged (Report to Government of 
India, 1908). 

Apart from the retention of indoxyl by the 
residual plant in the steeping vat, and the 
mechanical carrying over of indigo by the ' seet ' 
water, the deficiency of colouring matter is 
chiefly to be attributed to the conversion of 
indoxyl into products other than indigotih. 
Rawson {l.c.) has pointed out that if the fer- 
mented liquid is allowed to stand before oxida: 
tion a considerably decreased yield of indigo is 
ultimately observed. Thus, On the large scale, 
by standing for 6 hours a loss of 16-1 p.c. was 
apparent. Perkin and Bloxam {I.e. ) have found, 
as a result of their experiments with pure indican, 
that this alteration or * decay ' of indoxyl 
takes place not only in this manner during the 
fermentation process, but they consider that the 



INDIGO, NATURAL. 



indoxyl from the moment of Its production by 
the hydrolysis of indican until its final conver- 
sion into indigotin is continually sufiering this 
alteration. This peculiar reaction, representing 
an important defect in natural indigo manufac- 
ture is according to these authors, considerably 
inhibited by the presence of acid. 

COMMEECUL NaTTTRAI, InDIOOS. 

When natural indigo was at its zenith very 
numerous varieties of this dyestuff were placed 
on the market, but more recently, owing to its 
severe competition with the artificial colouring 
matter, many of these are now rarely met with. 
From Asia came the indigos of Bengal, Oudh, 
Madras, Java, Manilla ; from Africa those of 
Egypt and Senegal ; and from America those of 
Guatemala, Caracas, Mexico, Brazil, South 
Carolina, and the Antilles. 

The best varieties are the Bengal, Java, and 
Guatemala, although in England the Bengal is 
now mainly employed. Java indigo, formerly 
largely esteemed for the manufacture of indigo 
ejrtract, chiefly because of its general purity, 
at the present time appears to find its market 
chiefly in the East. 

A good quality of natural indigo has a deep 
violet-blue colour ; it acquires a coppery lustre 
when rubbed with the finger nail; it is light, 
porous, adhering to the tongue, and can be 
readily broken and ground. Low qualities, 
which contain much extractive and mineral 
matter, are duU and greyish in appearance, heavy, 
tough, and hard, and do not become bronzy by 
rubbing with the finger nail. 

Synthesis of iNDiGoim. 

In attempting to reconvert the oxidation 
product isatin into indigotin by reduction, 
Baeyer and Knop (1865-66) obtained succes- 
sively dioxindole CgH^NOj, oxindole CsH,NO, 
and, finally, indole C,H,N (Annalen, 140, 29). 
This last product, which is to be regarded 
as the parent substance from which indigotin 
is derived, was prepared synthetically in 1869 
by Baeyer and Emmerling by heating a mixture 
of nitro-cinnamic acid, caustic potash, and iron 
filings (Ber. 2, 680). In 1870 these same 
chemists succeeded in producing indigotin from 
isatin by heating the latter with a mixture 
of phosphorus trichloride and acetyl chloride. 

Already in .1869 (Ber. 2, 748) Kekule' sug- 
gested, but did not prove, that isatin might be 
an inner anhydride of o-amino-phenyl-glyoxylic 

acid C,H4<^jTTr . In 1878 Baeyer and 

Suida prepared oxindole synthetically from o- 

aminophenylacetic acid C8H4<^jj' , of 

which they proved it to be an inner anhydride ; 
and in the same year Baeyer produced isatin 
from oxindole, thus completing the chain of 
transformations necessary to prepare indigotin, 
artificially from coal tar (Ber. 11, 582, 684, 1228). 

Oxindole C|jH4<r / was first changed by 

the action of nitrous acid into nitroso-oxindole 
yCH(NO)-CO 



C.H«' 



\- 



■NH- 



, and this by reducing agents 



intoamino-oxindole CbHX 



CH(NHj)CO 

NH- 



126 



and this 



finally, by oxidising agents pr by nitrous acid, 
COCO 



/ 

NH 



A further synthesis of isatin, and therefore 
also of indigotin, was effected by Claisen and 
Shadwell in 1879 (Ber. 12, 350). By the action 
of silver cyanide on o-nitrobenzoyl chloride 
p TT ^-^COCl 



they obtained o-nitrobenzoyl 



successive 



cyanide C<,H«<^^^^, which, by 

treatment with hydrochloric acid and caustic 
potash, yielded the potassium salt of o-nitro- 

phenylglyoxylicadid CeH4<^^'^^°°^j this,by 

reduction in alkaline solution, gave the potas- 
sium salt of o-aminophenylglyoxylic acid 

CjH^r^jTii , which on the addition of acid 

' /COCO 

yielded isatin CjIIj^ / . In this manner 

the original view of KekuU concerning the 
constitution of isatin was verified. 

In 1880 (Ber. 13, 2259) Baeyer obtained 
indigotin in various ways from cinnamic acid, 
which already, in 1869, had been made to yield 
indole. By treating o-nitro-ciimamio acid 

„ „ ^^CH : CHCOOH 

^6"4<^Jir02 
with bromine, there is produced o-nitro- 
dibromhydrocinnamio acid 

~ „ ,^CHBr-CHBrCOOH 

l^6"l<OI0j 

which, on treatment with caustic alkali, yields 
o-nitro-phenyl-propiolio acid 

p „ ^^C;C-C00H 

On boiling this substance with caustic alkali, 
isatin is produced, but if reduced in alkaline 
solution — i.g. with glucose, or xanthates — it 
yields indigotin. This process was used indus- 
trially for some time for the production of o- 
nitro-phenyl-propiolio acid (propiolic acid), its 
transformation into indigotin being effected on 
the fabric (calico). 

Another method of changing o-nitro- 
phenyl-propiolic acid into indigotin is as follows 
(Annalen, 143, 325; 147, 78; 154, 137). It 
is first converted by boiling with water into 

0-nitro-phenyl-aoetylene ^6H4<rMo ' *''* 
copper compound of which, by oxidation with 
potassium ferricyanide, yields dinitro-diphenyl- 

diacetyleneCeH.^(|^^''^j^g^CeH4. Thisbody 

is changed by fuming sulphuric acid into its 
isomeride diisatogen 

/COCCCOk 
CeH/ /\ |\ >CeH„ 

^n-oo-n/ 

which, by reduction, yields indigotin 
/C0-C:C-C0\ 
CaH/ / \ >CeH4 

^NH Nir 

(Ber. 16, 60, 746). 



126 



INDIGO, NATURAL. 



Anothei of Baeyei'a iudigotin syntheses 
(D. R. P. 11857. 1880 ; Friedl. 127) is to treat o- 
nitro-cinnamic acid in alkaline solution with 
chlorine, whereby , there is produced o-nitro- 
phenylchlorlactic acid 

„ „ ^-^H(OH)CHaCOOH 

^»"«\N08 
which, by treatment with alkalis, changes into 
o-nitrophenylhydroxyacrylio acid 

Q2^(0H):CHC00H 

On heating this substance to 1I0°C. indigotin is 
produced. 

In 1882 (Ber. 15, 2856) Baeyer and Drewsen 
prepared indigotin from o-nitrobenzaldehyde 

C,H4<;^Q . If this substance is treated with 

acetone, acetaldehyde, oi pyroracemic acid, 
prodncte are formed which, under the influence 
of caustic alkali, readily yield indigotin. The 
reaction proceeds differently according to the 
reagent used. With the use of acetone the 
intermediate product is probably o-nitro- 
3-phenyI-lactic-methyI-ketone 

p jj _^CIH(OH)CHjCOCH, 

which, by the action of the alkali, yields indigotin 
and acetic acid. With acetaldehyde the 
intermediate body is o-nitro-phenyl-lactic-alde- 
hyde C.H.<«H(OH)CH..CHO^ ^„d ,1^3 ,^^ 

alkali decomposes to form indigotin and formic 
acid. With pyroracemic acid the intermediate 
substance is o-nitrocihnamylformic acid 

„ „ ^^CH : CH-COCOOH 

^'"'■^NOa 
which, under the influence of alkali, produces 
indigotin and oxalic acid. 

Seister, Lucius, and Briining (D. B. P. 
20255, 1882; Frdl. 142) patented a method 
similar to the first of the foregoing processes. 
Benzaldehyde and acetone are condensed ac- 
cording to CSaisen's method to form benzylidene- 
acetone (cinnamylmethyl-ketone) 

C.Hj-CH:CH-COCH,; 
this is nitrated, and of the para- and ortho- 
nitro- deriyatiTes thus obtained the latter is 
treated with alkali, and thereby yields indigotin. 
The yield is small, and the process was soon 
abaiidoned. The same firm tdso' patented the 
manufacture of m-methyl-indigotin by the follow- 
ing method, nitrating m-methylbenzaldehyde 
and treating the o-nitro- derivatiTe produced, 
with alkali according to Baeyei and Drewsen's 
method given above. The methyl-indigotin 
obtained ia very similar in appearance to in- 
digotin, but is remarkable for its solubility in 
alcohol. 

In 1882 (D. R. P. 21592, 1882 ; Frdl. 138 ; 
Ber. 17, 963) Baeyer and Bloem prepared 
indigotin from o -amino acetophenone 

and from o-amino phenyUcetylene 
p„ J-0=CH 

The acetyl derivatives of either of these sub- 
stances are dissolved in carbon disulphide and 
treated irith bromine in the cold. On dissolving 



the bromine compound thus produced, in con- 
centrated sulphuric acid, hydrobromic acid is 
evolved, and a colourless body is precipitated 
which, by the action of alkalis, decomposes to 
form indigotin. To ensure success the bromine 
must enter the methyl group of the acetyl-o- 
aminoacetophenone, and this takes place ii Ihe 
bromine acts in presence of cone. Hj,S04 or in the 
dry condition. If the bromine enters only the 
benzene group (and this occurs when operating 
in aqueous or glacial acetic acid solutions), no 
indigotin is obtained ; if the bromine enters 
both the methyl and the benzene groups — e.g. 
by worldng yrith chloroform solution — ^then 
brom-indigotin is ultimately obtained. During 
the formation of the indigotin in the subsequent 

/C(OH)!CH 
process, indozyl CjH.v ...-^-^ occurs as an 

^NH 
intermediate product. 

Gevekoht obtained indigotin by the prolonged 
action of an excess of ammonium sulphide on 
a cold alcoholic solution of o-nitro-brom- 
acetophenone containing the bromine in the 
methyl group, and finally evaporating the solu- 
tion (Annalen, 221, 330 ; D. R. P. 23785, 1883 ; 
Frdl. 139). This method is probably essen- 
tially the same as that of Baeyer and Bloem, 
since the first action of the ammonium sulphide 
is no doubt to produce o-amino-brom-aceto- 
phenone. 

P. Meyer (Ber. 16, 2261; D. R. PP. 25136 
and 27979, 1883; Frdl. 148, 149) obtained 
indigotin or substituted-indigotins by first pre- 
paring isatin or substituted-isatins, and tnen 
reducing their chlorides by means of zino 
or hydrochloric acid in glacial acetic acid in 
the manner previously known. If 1 molecule 
dichloracetio acid is heated with 4 molecules 
aniline there is produced the intermediate 
substance phenyl-imesatin, which, by boiling 
with strong acids or bases, yields isatin, thus : 
C,H5NO-N(C,H5)+H,O^C^H5NO,-fC.H5-NH,. 
Fhenylimesatin. Isatin. 

If in place of aniline in this reaction a p- 
monoamine is employed, eg. })-tOluidine, the 
Intermediate product obtained is p-toluyl-p- 
methylimestan oi p-methylisatin-p-toluyfimid 
CsH4(CH,)N0N(C,H,), and this yields by the 
action of acids or alkalis methylisatin 

0,H,(CH»)NO, 
and tolnidine. 

In consequence of Baeyer's synthesis of itidoh 
from o-nitro-cinnamic acid (Ber. 2, 680), its 

yCH:CH 
constitution is regarded as being CjHj^ / . 

Claisen and Shadwell's synthesis of isatin, already 
referred to, indicates its constitution as 
/COCO 

but numerous observations of Baeyer show 
that it contains a hydroxyl group, and 

/COC(OH) 
that its formula is C,Hi< ^ 
^N 

stitution products, however, it appears to exist 
in the above pseudo form. 



In its Bub> 



INDIGO, ARTIFICIAL, AND INDIGOID DYESTUFFS. 



127 



/COC(OH) 
Isatin C.H,/ ^ may be obtained by 

oxidation of indigotin with chiomio acid or 
nitric acid (J. pr. Cliem. p.] 24, H ; 25, 434) ; by 
tlie oxidation of amino-oxindole or of carbostyrU 
(Ber. 11, 1228; 14, 1921); by boiling o-nitro- 
phenylpropiolio acid with caustic alkali (Ber. 13, 
2259)'; and according to other methods already 
given. It's constitution is that of an inner 
anhydride of o-amino-phenylglyoxylic acid (Ber. 
12, 350). It forms orange-red prisms ; m.p. 
20<)°C. With thiophen it forms a blue colouring 
matter called indophenin (C,,H;NOS) (Ber. 18, 
2637). By the action of mlute nitric acid it 
yield^ nitro-salicylic acid. Heated with caustic 
alkali it gives aniline. Beduced with ammonium 
sulphide, isatid (CisHijNj04) is formed (J. pr. 
Chem. [i.] 24, 11 ; 25, 434). It combines with 
hydroxylamine to form nitroso-oxindol (Ber. 16, 
518,.17I4 ; Annalen, 140, 29). 

Isaflnic acid OeH4<^^^°*'^, in the form 

of its salts, is obtained by heating isatin with 
strong caustic alkali or by reduction of o- 
nitro-phenyl-glyoxylic acid. Only its salts are 
stable, the free acid decomposing into isatin and 
water, by merely boiling its aqueous solution. 
Its constitution is that of o-amino-phenyl- 
glyoxylic acid (Ber. 12, 350). 

/COC-COOCaHs 

Isatogenie acid ether C.H,^ /\ 
\ N-O 
(Ber. 14, 1741 ; 16, 60, 746) is produced by 
the action of concentrated sulphuric acid on 
o-nitro-phenylpropiolic-aoid-ether, with which it 
is indeed isomeric, . It forms yeUow needles : 
m.p. 115°C. 

CO'C'C'CO 

DUsatogen C.Hy /\ |\ \0eH4(Ber. 16, 
\N0 0-N/ 
50, 746) is obtained by the action of concentrated 
sulphuric acid on dinitro-diphenyldiacetylene. 
It forms red needles, soluble only in chloroform, 
nitrobenzene, and concentrated sulphuric acid. 

A. G. P. 

INDIGO, ARTIFICIAL, AND INDIGOID 
DYESTUFFS. The elucidation of the constitu- 
tion of indigo, the result of the brilliant and 
indefatigable researches of A, von Eaeyer 
{v. fwprd)^ has led to consequences of extra- 
ordinary importance. The methods discovered 
for the synthetical production of indigo 
offered at first little or no prospect of the 
artificial production of this most important 
dyestnfi at prices which could compete with 
the natural product. But the patient and 
unceasing work carried on for that purpose 
in the laboratories of the Badische Anilin- & 
Soda-Fabrik in Ludwigshafen gradually sur- 
mounted the existing difficulties. Artificial 
indigo appeared in the marliet in the year 1897, 
and was soon acknowledged to be cheaper, purer, 
and more easy of application than the natural 
product. New syntiietical manufacturing pro- 
cesses which have since then been introduced, 
combined with a strong competition between 
the various manufacturers, led to a steady 
reduction of prices, so that at present (1911) 
the synthetical dyestufi may be said to have 
driven out the natural one everywhere, even in 



countries in which the indigo plants are grown, 
such as India, the Dutch colonies, China, Japan, 
and South America. The history of artificial 
alizarin has been repeated in all its details in 
the progress of artificial indigo. But the con- 
sequences of tljis new triumph of synthetical 
chemistry have gon« further, in that they have 
revolutionized the old-established European 
industries engaged in the production as well as 
the a^pplication of artifioiafdyestufis. 

The old, but difficult and uncertain process 
of vat-dyeing, necessary for the application of 
indigo, has been carefully studied by the fac- 
tories which had taken up the production of 
the synthetical product. Sodium hydrosulphite, 
long known to be the "best means for reducing 
indigo in the vat, but unstable and difficult to 
prepare, has been brought into new forms in 
which it is quite stable and easily applied. 
Thus vat-dyeing has become an operation 
almost as easy and simple as any other process 
of dyeing, and the consumers of artificial 
colouring matters became anxious to be furnished 
with products similar to indigo in its mode of 
application and its fastness, but differing in 
shade. This wish has been satisfied almost 
simultaneously with its being felt. A large 
and constantly increasing number of new vat- 
dyes of every conceivable |hade has been offered 
to the dyer and calico-printer, who is able to 
use them jointly or in mixtures with indigo, 
and thus to produce goods, the shades of which 
are quite as durable as the fibre itself. Some ~ 
of the new vat-dyestuffs not only equal, but 
actually exceed indigo in fastness to light, air, 
and all the other influences which attack and 
destroy the colour of dyed fabrics. The intro- 
duction of the new synthetical vat-dyestuffs has 
inaugurated a new epoch of fast dyeing, the 
full importance of which will only be recognised 
in time to come. 

The synthetical manufacture of new colour- 
ing matters similar to indigo in their properties 
was at first the natural consequence of the 
numerous new syntheses of indigo itself 
gradually discovered by various Chemists, and 
many of which proved applicable to the produc- 
tion of compounds sinular to indigo in their 
constitution, but differing from it in certain 
details of composition, and consequently also 
in their shades. Many of these substances 
could be made on a large scale, and offered to 
the consumer at moderate prices. They are 
now known under the name of ' Indigoids,' and 
the more important of them will be mentioned 
further on. 

The investigation of indigo and the indigoid 
dyestuffs led, however, to another result of no 
small importance. The connection existing 
between the constitution and the properties of 
indigo as a dyestuff, so long a mystery, was at 
last recognised, and the atomic configuration 
was disclosed which causes a dyestuff to be 
applicable to vat-dyeing. The natural conse- 
quence of this discovery was the possibility of 
producing, by synthetical methods, a vast 
number of new vat-dyes, which in their constitu- 
tion have no longer any similarity to indigo, 
and the majority of which has been derived 
from anthraquinone, the mother-substance of 
alizarin, which has thus assumed a new im- 
portance. 



128 



INDIGO, AETIFICUL, AND INDIGOID DYESTUFFS. 



The description of these dyestnfis supple- 
menting indigo in its applications, and now 
abeady exceeding the incUgoids in number is 
dealt with elsewhere {see Vat-dyes, Mobeen; 
Indanthrenx). 

The number of vat-dyes now already in 
practical use or in the stage of bSing introduced 
may be estimated at from 80 to 90, and is con- 
stantly increasing. Their discovery is due to 
the inventive genius of many chemists, amongst 
whom Bene Bohn may be considered as we 
pioneer. 

A. Altiflelal indigo. The constitution of 
indigo is expressed by the formula : 

N/^nh/ \nh/\/ 

Of the numerous methods which lead to the 
synthetical production of such a compound very 
few are applicable to its manufacture, and only 
the latter will be here mentioned. 

The first attempt at a technical synthesis of 
indigo was made in 1880 by A. von Baeyer in 
his German patent 11867, which was sold to 
the Eadische Anilin- & Soda-Fabrik and the 
Hochster Farbwerke jointly. In this ortAoni- 
trocinnamic acid is used as a raw material, and 
transformed into indigo by three different 
methods. Of these only the one which passes 
through ort;'.onitrophenylpropiolie acid as an 
intermediate product found for a short time 
a limited and almost experimental application 
as a means of producing indigo on the fibre in 
calico-printing. 

Another method (1882), which consists in 
adding caustic soda to a solution of o-nitro- 
benzaldehyde in acetone, when the methyl-o- 
nitrooinnamylketone formed as an intermediate 
product is immediately condensed into indigo, 
was also, in spite of its simplicity, unable to 
compete with the natural product. 

ia 1890 K. Heumann observed that phenyl- 
glycine and its ortAocarboxvlio acid are trans- 
formed into indoxyl and indoxylcarboxylic acid 
by being melted with caustic potash ; the orange- 
coloured melts obtained yield indigo on being 
o^dised with air in aqueous solution. The 
patents obtained for these reactions (D. B. P. 
54626 and numerous additions ; also D. B. P. 
66273 and additions) passed into the hands of 
the Badische Anilin- & Soda-Fabrik, but were 
not considered very promising by the majority 
of chemists. Tet they were destined to assume 
fundamental importance in the subsequent 
development of the indigo industry. It is true 
that a good many other inventions were necessary 
to raise them to that position. 

Indoxyl and indoxylcarboxylic acid have the 
constitution expressed by the formulae : — 



Y 



\/C0\ 



\/\nh/ 



CHj and | 



C0\ H 

c 
\/\nh/'^cooh 



These formulsD represent the so-called 
' pseudo '-forme, which are the first products 
of the reaction. Isolated indoxyl and indoxyl- 
carbonio acid are better represented by the 
tautomesic formulae : 



C-OH 



(X> ^" CO 



C-COOH 



(Baeyer.) 

On being treated with atmospheric oxygen 
in alkaline solution the one loses E, in the 
shape of water, the other HjCOg in the shape 
of carbonic acid (HjCOg), and the so-called 
' indigo bridge ' >C=C< is formed by two such 
indoxyl complexes being united by double 
valencies. 

Phenylglycine and its or/Aocarboxylic acid are 
prepared by the action of monochloracetic acid ' 
upon aniline and anthranilic acid : — 



NH, 



CHjCl 
■I 
COOH 



NH— OH,— CO-OH 

I 



/\+L-_=Hci+, 



V 



COOH 



NH, NH—GHj— CO-OH 

1 CH^a I 

r/\cOOH+J,„„„=^^+|/\-CO-OH 

It was observed, that phenylglycine-o-car- 
boxy'io acid gave better yields of indigo than 
phenyl-glycine itself, which was, on the other 
hand, cheaper and more easily accessible. Later on 
it was found that both these glycines are capable 
of being transformed into indigo with very good 
yields S every trace of water is excluded from 
the alkaline melt. The glycine itself is in this 
respect more susceptible than its carboxyl 
derivative. Not only the water invariably 
retained by all the caustic alkalis hinders the 
reaction, but also the water formed in the 
reaction itself. One of the means of over- 
coming this difficulty consists in the addition 
of finely ground, lime or baryta to the 
melt. 

In taking up the manufacture of artificial 
indigo by Heumann 's method in the beginning 
of the nineties the Badische Anilin. & Soda- 
Fabrik decided to use phenyl^ycine-o-carboXylic 
acid as a raw material. This decision was 
prompted not only by the better yields which 
were obtained from this / product, but ev^n 
more so by considerations of quite a different 
nature. 

If it had been necessary to produce the 
anthranUio acid requilred for the manufacture 
of indigo by the oxidation of o-nitrotoluene 
and subsequent reduction of the o-nitro- 
benzoio acid thus obtained, aU the toluene 
produced by the distillation of coal-tar would 
probably not have been sufficient for the 
purpose. There is, however, another way of 
producing anthrai41ic acid which consists in 
treating phthalimide with alkaline hypochlorites 
(Hoogewerff's and Van Dorp's process ; D. E. P. 
55988, Badische Anilin- & Soda-Fabrik, 1890). 

> Instead of this acid, prepaii?d in the old maimei 
from acetic acid and chlorine, ethyl monochloracetate 
may be used, which can be obtained from acetylene by 
a simple process (D. &. PP. 1S4667, 171900. 216940, 
209268, 210502, and 216716, Imbert and Consortium 
Wr electrochemlache Industrie, Namberg). See also 
Chemikerzeitung, 1911, p. 1063. 



INDIGO, ARTIFICIAL, AND. INDIGOID DYESTDPFS. 
NH-CH.COONa 



129 



f>htliaIiiDide is easily obtained by treating 
phthalio anhydride with ammonia. Phthalio 
acid, on the other hand, is beat prepared by the 
oxidation of naphthalene. 

Thus it became possible, by using phenyl- 
glycine-o-carboxylio acid as a starting-point for 
the synthesis of indigo on a large scale, to base 
this marufaoture on the use of naphthalene as 
its firat raw material, a hydrocarbon which is 
contained in coal-tiar in much larger quantities 
than any other of its constituents. 

Even when these conclusions had been arrived 
at a great deal remained stiU to be done. It is 
now known that the Badische Anilin- & Soda- 
Fabrik had to invest about 1,000,0002. in experi- 
ments and new plant before artificial indigo 
could enter the world's market as a rival to the 
natural product, and that the ultimate success 
obtained is mainly due to the courage, inventive 
genius and perseverance of BudoU Enietsch, 
who superintended the whole development of 
this new industry. But it must also be said that 
the latter found its advent well prepared by 
the development which chemical industry as a 
whole had taken towards the end of the nine- 
teenth century. One of the principal advan- 
tages produced by that development was the 
possibility of obtaining chlorine (which is re- 
quired both for the chloracetic and the anthra- 
nilic acid used in the indigo process) and caustic 
alkaUs at extremely low prices owing to the 
introduction of the electrolytic decomposition 
of alkaline chlorides. 







4-NaNHj=] I CHj+NajO-fNH, 



Sodamide. 



-co/ 

Indoxyl 
(pseudo- 
lorm). 



Sodium o^de. 



The oxidation of naphthalene into phthalio 
acid as practised in former times was cum- 
brous and difficult, and gave very poor yields. 
A new method was discovered for the pur- 
pose which consists in the oxidation of naph- 
thalene polysulphonio acids by means of very 
strong pyrosulphuric acid. To obtain the 
latter a new process had to be worked out, now 
known to the world as the catalytic or contact 
process (see SuuHmuo acid). A certain 
quantity of mercuric sulphate must be added 
in the oxidation of the naphthalene sulphonio 
acid ; its action is purely catalytic and inde- 
finite. The sulphur dioxide formed by the 
reduction of the pyrosulphuric acid returns 
continuously into the manufacture of the latter. 
The oxidation of the naphthalene thus prac- 
tically takes place by means of atmospheric 
oxygen, and phthalio anhydride is exceedingly 
cheap ii manufactured on a large scale by tim 
process. 

The employment of naphthalene as a raw 
material rendered it possible for artificial indigo 
to compete commercially with the natural 
product. But it was destined to meet itself 
with a very serious competition which arose 
from a discovery made by J. Pfleger of the 
Deutsche (Sold- & Silber-Scheide-Anstalt in 
Frankfurt o/M., who observed that the de- 
structive influence of water in the alkali melt 
of phenylglycine could be completely elimi- 
nated by using, not sodium hydroxide, but 
sodamide for effecting the transformation of 
the glycine into indoxyl. Sodium oxide 
and getseous ammonia are instantly formed 
by the water produced in the condensation 
of the glycine according to the following 
reaction : — 
Vol. Ill— T. 



Sodium 
salt of 
phenyl- 
glycine. 

The low melting-point of sodamide, which 
may_ be diluted with potassium or sodium 
cyanides (which also have a low melting-point) 
makes it possible to carry out the process at 
the low temperature of 180''-230'' 0. which 
favours the production of almost theoretical 
yields. Of course the process is also appUoable 
to the transformation of phenylglycine-o-car- 
boxylio acid into indigo. 

It is true, that sodamide can only be 
prepared by the action of ammonia upon 
metallic sodium ; its price is therefore a lugh 
one ; on the other hand, the advantages to be 
obtained by its use are very great and make it 
possible for this process to compete with the one 
adopted by the Badische Anilin- & Soda-Fabrik. 
It was therefore acquired by the Hochster 
Farbwerke, who are now producing a con- 
siderable share of the world's consumption of 
indigo. 

The enormous increase of the world's pro- 
duction of benzene, caused by the general 
introduction of by-product coke-ovens, and the 
very low prices of aniline caused by this over- 
production, has also favoured the success of 
Pfleger's invention. 

Other synthetical methods have been de- 
vised wliich lead from aniline to indigo, such as 
Sandmeyer's and Blank's. But they cannot 
compete with the methods described, and have 
therefore never been carried out on more than 
an experimental scale. For details about these 
processes, some of which are exceedingly 
interesting from a theoretical point of view, the 
existing works on the chemistry of colouring- 
matters and more especially the patent literature 
should be consulted. Some of these processes 
may possibly assume considerable importance 
as a means of producing indigoid dyeatufEs. 

The complete insolubility of ini^go in water 
and aqueous fluids makes it imperative that the 
dyestuS should be in a state of extremely fine 
subdivision, and thoroughly moistened before 
being Introduced into the vat. For this reason 
the dyers used to grind the natural product with 
a certain proportion of water in the well-known 
indigo-miUs. The unnecessary trouble caused 
by tliis preliminary treatment is spared by the 
form which has been given to the artificial 
dyestufl, which is generaUy sold in the shape of 
a paste containing 20 p.c. of pure indigotin. 
For export, where the reduction of carriage, 
and in many countries also the import duties, 
have to be considered, stronger pastes may be 
prepared or even the shape of a dry powder is 
-chosen. Much trouble has been taken to reduce 
the indigo to the greatest possible fineness. All 
the modem means of powdering and grinding 
have been utilized, and also the method of 
precipitating indigo from its solution in sul- 
phuric acid (in which it is contained as a 
sulphate) by the addition of water has been 
resorted to. 



INDIGO, ARTIFICIAJ,, AND INDIGOID DYESTUFFS. 



130 

The world's annual consumption of indigo is 
estimated at more than 6,000,000 kilograms of 
the pure dyestuff. In 1900, that is three years 
after its introduction, the artificial product had 
secured about one-tenth of this quantity. At 
present the natural product is almost entirely 
Bupefseded by the artificial one, and vast tracts 
of land formerly devoted to its cultivation have 
become available for the production of rice and 
other cereals. 

The valuable properties of indigo as a dye- 
stufi are a function of the peculiar atomic con- 
figuration which connects the two phenylene 
radicles. By the reduction in the vat 2 atoms 
of hydrogen are taken up by this complex and 
indigo white is formed, the exact constitution 
of which is doubtful. But it is now generally 
aclmowledged, that in leuco -indigo hydroxyl 
groups have replaced the ketonic oxygens of 
indigo. These hydroxyl groups possess auxo- 
chromio characters, and are responsible for the 
absorption of the indigo white by the fibre. It 
follows that every other strongly coloured 
aromatic substance which contains at least two 
reducible caibonyl groups must be endowed 
with the properties of a vat-dye. This con- 
clusion has been strictly confirmed by modern 
investigations and the whole modem develop- 
ment in the production of vat dyes has been 
built up on it. 

B, Indigoids. — The congeners of indigo may' 
be divided into two different classes. One of 
them contains the true derivatives of indigo, in 
which one or more of the 8 hydrogen atoms 
of the two phenylene groups are replaced by 
other Bubstitueuts ; the other embraces sub- 
stances which are strictly analogous to indigo 
in their constitution but different from it in 
the construction of the complex connecting the 
two phenylene groups, which in this case as well 
as in that of indigo may have their hydrogen 
atoms replaced by other substituents. An 
enormous variety of new dyestuffs may thus be 
synthesised, all of which contain the char 
racteristic chromophorio group of indigo : 

—CO— 0=0— CO— 

I I 

(a) Substitution products of indigo. — These 
may be prepared by treating indigo with suit- 
able reagents or by using suitably substituted 
ingredients in any of the synthetical methods 
for the production of indigo. 

One group of these substitution products has 
been known for almost a century, and used 
formerly to be manufactured from natural 
indigo, viz. the sulphonic acids derived from it, 
commonly known under the name of Indigo 
Carmine. As these cannot be used as vat- 
dyes, they need only be mentioned here. They 
are now invariably prepared from artificial indigo 
and still used to a moderate extent in wool- 
dyeing, although they have been largely super- 
seded by other soluble blues. Though derived 
from on? of the fastest dyestuffs Imown, the 
indigosulphonio acids are, strangely enough, of 
an extremely fugitive nature. 

The halogen derivatives of indigo are very 
numerous, As many as six atoms of ohlorina 
or bromine lUay be introduced into the molecule 
of indigo. The properties of the products thus 
obtained, their shade and fastness, vary strongly 



not only with the number of halogen atoms 
introduced, but also with their relative position 
in the molecule. Of the mono- and di-sub- 
stituted indigos those which contain their 
halogen atoms in the y-position to the imino 
groups are very similar to indigo itself ; those, on 
the other hand, in which the j)-positions to 
the keto groups are taken up are no longer 
blue but reddish-violet in shade. The di- 
bromo-indigo corresponding to this condition 
has been proved by Friedlander to be identical 
with the purple of the ancients iq.v.). In spte 
of the fame which this dyestuff once possessed 
modem industry has not thought it sufSeiently 
valuable to be introduced into commerce. 

If more than two atoms of halogen be intro- 
duced into the molecule of indigo the dyestuffs 
obtained become more and more brilliant and 
greenish in shade. The first of these valuable 
dyestuffs introduced was tetrabromo-indigo ; it 
was prepared by the Gesellschaft fiir Chemische 
Industrie in Basle and brought out as ' Ciba '-blue 
— ' Ciba ' being the distinctive name adopted for 
all the vat-dyes of this factory. The oorre- 
spending tetrachlorinated derivative is 'BriU 
lant indigo 2B' of the Badische Anilin- & 
Soda-Fabrik. Penta-and hexabromo -indigo are 
still more greenish, and are now being manu- 
factured by various firms. 

It is, of course, also possible to substitute 
some of the hydrogen of the indigo molecule by 
organic radicles. Thus we come to the homo- 
logues of indigo, several of which have been pre- 
pared. They are all very similar to indigo and 
offer no special interest. This is also the case 
with naphtylindigo, the shade of which is a 
dull green. Its dibromo derivative is much 
clearer in shade ; it has been brought out as 
'Ciba-Oreen 0' by the Basle firm already 
mentioned, 

(b) Indigoids, in which the central complex 
differs from thai of indigo. — In order to under- 
stand the nature of these compounds we must 
reconsider the constitution of indigo. It con- 
sists of two phenylene groups, linked together 
by the complex 

—CO 



-CO-.. ^ .,^0- 



Now in this complex the group -C0-C=O-C0- 

I I 

is the indigo ohromophore which connects all 
these dyes, into one family and it cannot be 
touched .or altered without destroying the 
■whole character of the compound and its nature 
as a vat-dye. It follows, that the only changes 
possible in the central complex of the indigo 
molecule must be confined to the two imino 
groups, which may either be altered by their 
hydrogen being substituted, or by their being 
shifted into other positions, or by being entirely 
replaced by other atoms or atomic complexes. 
All these changes have been accomplished. 

As an interesting example of the first of these 
alterations two dyestuffs may be mentioned: 
Ciba-Tellow and Ciba-TeUow 00. They 
are prepared from indigo and tetrabromo-indigo 
by the substitution of two benzoyl groups fo'r 
hydrogen in the imino groups. The constitu- 
tion of Ciba- Yellow G is thus expressed by the 
formula : — 



INDiaO, ARTIFICIAL, AND INDIGOID DYESTUFFS. 



131 







I ^; 



C=0 



COy. 







Benzoyl chloride does not act upon indigo under 
ordinary oircumstances, but if a trace of metallic 
copper be added, its catalytic action causes the 
substitution of the hydrogen by the benzoyl 
group. This interesting" manufacturing process 
has been invented by G. Engi. 

If the imino groups are to be shitted or to be 
exchanged for other complexes, this cannot be 
done by starting from ready-formed indigo. 
The new dyestuS has to be buHt up syntheti- 
cally. According to the synthetical methods 
adopted we can obtain indigoids of either 
symmetrical or asymmetrical constitution. 

One of the first instances of such a synthesis 
was the process by which A. von Baeyer prepared 
Indirubin, the red dyestuff always contained in 
natural indigo and first observed by Berzelius. 
This substance is formed it alkaline solutions 
of indoxyl and isatin are mixed in the cold — 



\y 



Indoxyl 



I— CO- 



;— CO- 



^. 



&COH 



Isatin. 



,/V-co- 



/COn 



M I. 



/C^H>C=<_>NH+H,0 

o 



Indirubin. 



Indirvhin is an, assymetrjcal indigoid in 
which both the chromophorio complex and the 
two imino groups are still preserved, but they 
have changed their relative position in the 
molecule. Indirubin is of no value as a dye- 
stuff, but its tetrabromo derivative, prepared 
by G. Engi, is a useful violet and sold under the 
name Ciba-Hdiotrope. 

If the imino groups are to be exchanged for 
other divalent complexes, oxygen suggests 
itself as a suitable substituent. ' Oxygen 
indigo ' has been prepared by Friedlander, 
but it proved to be a very poor dyestuff. But the 
same chemist observed in 1906, that sulphur, 
introduced into the position of the imino groups 
in indigo, has an excellent effect. A dyestuff of 
a deep bluish red shade and extraordinary 
-intensity and fastness is formed, which is now 
known as Thioindigo red and manufactured by 
several firms. It was the first reaUy applicable 
red indigoid and the process by which Fried- 
lander first prepared it was protected by the 
German patent 194237 by Kalle & Co. who 
bought Friedlander's invention. This process is 
in all its stages strictly analogous to the syn- 
thesis of indigo from phenylglycine-o-carboxylic 
acid, but the nitrogen occurring in the latter 
is everywhere replaced by sulphur. Thus in the 
first stage authranilio acid is replaced by thio- 
salicylio acid — 



o 



■NH, 
COOH 



Anthranilic acid. 



I j— COOH 



Tbiosallcj'Uc acid. 



The latter is. treated with monochloracetio 
acid, and thus transformed into 

/^-S— CHj— COOH 
'^ J— COOH 

Phenylthioglycine-o-caiboxylicacid. 

which is, of course, quite analogous to 

/\-NH— CHj— COOH 
L J— COOH 
Phenylglyoine-o-caiboxylic acid. 

By melting with caustic soda thioindoxyl- 
oarboxyhc acid — 






-co 



€H— COOH 



is formed, which, on being oxidised, yields 



30-^' 



0=CC 



-s- 



Thioindigo Red. 

This process may be simplified by an inven- 
tion described in the German patent 187586 of 
the Gesellschaft ftir Chemische Industrie in 
Basle, according to which the phenylthioglycine- 
o-carboxylio acid is simply boUed with nitroben- 
zene. Condensation and ozydation take place 
simultaneously and the red dyestuff is deposited 
in glistening crystals. 

Another extremely simple method for the 
production of this dyestufi has been invented 
by E. Miinoh, and patented by the Badische 
Anilin- & Soda-Fabrik (French Pat. 385044; 
German Pat. application B. 47813). It consists 
in treating the salts of thiosalicylio acid with 
dichloroethylene. This compound, as a, rule so 
reluctant to part with the chlorine it contains, 
in this case acts most readily, connecting two 
molecules of the acid, thus forming the whole 
chain of atoms required — 

/\/^S— C=C— S\,/\ 



KJ 



\ 



H H 
COOH HOO 



J\/ 



By treating this product with ohlorosulphonio 
acid two molecules of water are eliminated, and 
the central complex of thioindigo red is formed. 
It suffices to add water which precipitates the 
dyestuff in a very pure condition. 

Thioindigo red is extremely fast, but un- 
fortunately its shade is not favourable to a 
very large consumption. An indigoid of a 
brilliant scarlet shade was required, and this 
was found in the asymmetrical representative 
of this group. 

Thioindigo Scarlet. — ^This compound is ana- 
logous to indirubin in the same way in which 
thioindigo red is analogous to indigo, and it is 
also prepared by the method suggested by this 
analogy; thioindoxyl — 



(or, as it is often called, oxythionaphthene) is 
treated in an alkaline solution with isatin (see 



132 



INDIGO, ABTIFICUL, AND INDIGOID DYESTUFFS. 



equation for the formation of indirubin). 
has consequently the constitution 
/COx 



0=i 



^■>c= 



>NH 



.0 

and is not only asymmetrical, but also a mixed 
indigoid, containing both sulphur and the imino 
group. 

Both thioindigo red and scarlet yield many 
new dyestufis b^ the substitution of halogens 
and other substituents for hydrogen in uieir 
phenylene groups. They dye various shades of 
scarlets, bluish reds, and reddish violets, and 
several of them have come into use as service- 
able vat-dyes. O. N. W. 
INDIGO COPPER. CuprieauVphidev. CovtsR. 
INDIRUBIN V. Indiqo, Naitiral; iNsiao, 
Aetificiai,; IndoxyIj compounds. 

INDIUM.. Symbol In. At.wt. 113-97 
(Winkler, Bimsen, Thiel, Mathers). Indium 
belongs to the aluminium group of the elements 
and was discovered in Freiberg zinc blende by 
Beich and Bichter in 1863 by means of spectrum 
analysis. It also occurs in small quantities in 
other zinc blendes, in siderite, and in various 
manganese ores (Hartley and Bamage, Chem. 
Soc. Trans. 1897, 633). The metal can be ob- 
tained from the oxide by ignition in a current of 
hydrogen or by fusion with sodium (Winkler, 
J. pr. Chem. 1867, 102, 273). It can also be 
obtained pure electrolytically from the chloride, 
nitrate, or sulphate (Dennis and Geer, Ber. 1904, 
37, 961 ; Thiel, ibid. 175 ; Mathers, J. Amer. 
Chem. Soc. 1908, 30, 209). 

Indium is a white, readily malleable metal, 
softer than lead, and is not attacked by air at 
ordinary temperature. It can be obtained as 
regular octahedral crystals (Sachs, Zeitsch. 
Kryst. Min. 1903, 38, 495; Thiel, /.c), having 
sp.gr. 7-12 at 1374°, and m.p. 155°. It dissolves 
slowly in hydrochloric or sulphuric acids but 
readily in nitric acid, and when heated in- the 
blowpipe ^ves a blue colour and an incrustation 
of the oxide. Indium forms a series of iso- 
morphous mixtures with lead (KumakoS and 
Pushin, J. Rusa. Phys. Chem. Soo. 1906, 38, 
1146 ; Kumakofi and Schemtscliuschny, Zeitsch. 
anorg. Chem. 1909, 64, 149). It also combines 
with selenium and tellurium, forming black 
masses with a metallic lustre (Benz, Ber. 1904, 
37, 2110). In its compounds, indium appears 
as mono-, di-, and tri-valent, but only the latter 
are stable in aqueous solution. 

Indium oxide In^O, is a pale yellow powder 
which, according to Benz (Ber. 1903, 36, 1847), 
is converted into two other amorphous modifica- 
tions when strongly heated <Meyer, Zeitsch. 
anorg. Chem. 1905, 47, 281). At 1000° the oxide 
commences to volatilise and is partially converted 
into chlorine-green shining crystals (Benz, I.e. 
2751 ; Thiel, I.e. and Ber. 1906, 48, 201). The 
lower oxide, InO, possibly also exists. 

Indium I^droxide In(0H)3 resembles alumin- 
ium hydroxide, is converted into the oxide by 
heating, dissolves in potash but not in am- 
monia and readily forms colloidal solutions in 
the absence of electrolytes. 

Indium hydroxide behaves towards bases as 
a weak acid : when carefully dried at 100°, the 
tnela acid In-O-OH is obtained, and the corre- 



It spending magnesium indate (InO)]OjMg,3H20 
is formed by boiling a solution of indium ohioride 
with magnesium chloride (Benz, Ber. 1901, 34, 
2763 and I.e.). 

Halogen salts. Indium forms three chlorides, 
InCl, InClj) InCI, ; the last forms a crystalline 
compound with pyridine, 

InCl,-3C5H5N, 
m.p. 253° (Dennis and Geer, l.e. ; Rengade, 
Compt. rend. 1901, 132, 472). Three corre- 
sponding bromides (Thiel, Ber. 1904, 37, 176), 
a triiodide, the trifluorides, InFgjSH^O and 
InFj,9H20 (Thiel, Z.c. ; Chabri^and Bouohonnet, 
Compt. rend. 1905, 140, 90), an oxychloride 
InOCl, an iodate, and a percfUorate (Sohleuder- 
berg, J. Amer. Chem. Soo. 1908, 30,211)are known. 
Indium sulphide luiS, is a scarlet powder 
with metallic lustre which, when heated in 
hydrogen, forms the lower sulphide InS, which 
is a volatile brown powder. • Both sulphides can 
be obtained in a crystalline form (Thiel, I.e.). 

Basic indium sulphite In2(SO,)gIn,0,,8H20 is 
a crystalline powder which is obtained when an 
indium salt is boiled with acid sodium sulphite. 
Indium also forms svlpMtes, nitrates, the 
molybdaie In2(Mo04)8,2H20, the platino-cyan- 
ide In,[Pt(CN)4]3 (Benz, I.e.), a sdemte 
(Schleuderberg, I.e.), wanaie, tungstate, a^d 
sitico-tungstatea (Wyrouboff, BulL Soc. Franc. 
Min. 1907, 30, 277). 

Indium ammonium alum 

In,(SO,)a(NH4)jS04,24H,0 
(also with 8H2O) forms wdl-defined regular 
octahedra. Siiuilar alums are formed with the 
sulphates of rubidium and csesium, but the 
analogous salts with potassium and sodium are 
not pure alums (Chabri^ and Bengade, Compt. 
rend. 1900, 131, 1300; 1901, 132, 472). 

INDOFORM. Trade name for a mixture of 
salicylic acid) acetyl salicylic aoid, moistened 
with formaldehyde solution, dried, and perfumed 
with methyl salicylate (p. Sybthbtio DBtros). 

INDOINS (Safmnine azo- colouring matters). 
The name Indoin blue B is given to the basic 
tannin colouring matter which is formed by 
combining the diazonium salt prepared from 
safranine and nitrous acid with j3-uaphthol. 
The compound is of some technical importance 
and dyes both unmordanted and tannincd 
cotton fast indigo shades of blue. 

The name indoin was also given by Baeyer 
(Ber. 1881, 14, 1741) to a Dlue compound 
resembling indigo, having the composition 
CsjHjoOeNt, prepared by the aotion of reducing 
agents, for example ferrous sulphate, on phenyl- 
propiolic acid dissolved in sulphuric acid. 

J. F. T. 
INDOLES. To this class belong a series of 
compounds, many members of \mch are of 
considerable importance from the bio-chemical 
standpoint. 

They are derived from indole CjHjN, a com- 
pound which is related to indene in the manner 
shown by the following formulae : — 



/N/^)cH 

■CH, 

_ Indene. ^. 

The indole derivatives which occur in the 
organism are more or less closely related to 
tryptophan {q.v.), a substance which, according 




INDOLES. 



133 



to the latest inreBtigation is an indole-amino- 
piopionio aoid. 

Indole was first obtained by Baeyei by 
distilling, with zino dust, either ozindole 

C«H4<^jjj^^C0, or the product obtained by 

reducing indigo with tin and hydrochloric acid. 
It is also formed when o-nitrocinnamio aoid is 
distilled with caustic potash and iron filings 
(Baeyei and Emmerling, Ber. 1869, 2, 680) : 

It can also be produced by passing the vapour 
of ethyl aniline and other alkyl anilines through 
a red-hot tube (Baeyer and Caro, Ber. 1877, 10, 
692, 1262), but the best method of preparation 
is by the action of dichlorethei 

CHaaCHa-OOisHj 
on aniline. A mixture of 60 grams of aniline 
with an equal bulk of water is heated, and to 
the boiling liquid 25 grams of dichlorether are 
gradually added. The boiling is continued for 
an hour, after which the water and excess of 
aniline are distilled ofE and the residue is heated 
for about 4 hours at 210°-230°. On distilling 
the product with steam, indole passes over and 
may be purified by conversion into the piorate. 
In this reaction, ethylidene di-anUine is first 
formed which, on heating to a higher tempera- 
ture, breaks down ihto indole and aniline, 
thus.: 
C.H5N : 0H-ClH2-NHCeHB->>C8H,N4 OeHsNHj. 

Indole forms colourless, lustrous laminae, 
melts at 52° and boils with partial decomposition 
at 253°-254:°. It is readily- volatile in steam 
and is easily soluble in boiling water and in 
alcohol, ether, and benzene. When nitrous«g:Cid 
is added to an aqueous solution of indole, con- 
taining nitric acid, nitrosoindole nitrate is preci- 
pitated in the form of small red needles. An 
aqueous solution, or the vapour of indole, colours 
a pine chip moistened with hydrochloric acid 
and alcohol cherry red, the colour afterwards 
changing to reddish brown. Indole suspended 
in water and o^dised with ozone yields traces 
of indigo (Kencki, Ber. 1876, 8, 727). Indole is 
a weak base and forms, with concentrated 
hydrochloric acid, a sparingly soluble salt wliich 
is dissociated by boiling with water ; the piorate 
is precipitated as dark red needles when a solu- 
tion of indole in light petroleum is treated with 
picric acid. 

Acetyl indole CsHjNCGaHjO), which is formed 
by the action of acetic anny<£:ide, melts at 182°- 
183°. Indole accompanies scatole as a product 
of the putrefaction of albumen. 

Derivatives of indole. — The homologues of 
indole are most readily obtained by heating the 
phenyl hydrazones of ketones of the formula 

E'-COCH, or E'-COCHaR', 
or the phenyl hydrazones of the aldehydes of 
the formula E'-CHa'CHO, with zinc chloride at 
180°. The zinc chloride abstracts the elements 
of ammonia thus : 
C8HeNH-N:C(C5H,)j 
A.cetone phenylhydiazone. 

/S>Metfayliudole. 



but the reaction is difficult to express by means 
of structural formulse. Indole itself cannot be 
prepared by this reaction. 

IndoIe-3-piopionie acid (scatole acetic acid) 

/G-CH.-CH,CO.H 

This substance was isolated by Nencki (Monatsh. 
1889, 10, 506) from the products of the putre- 
faction of albumen. It has been synthesised by 
EUinger (Ber. 1905, 38, 2884) by -the action of 
alcoholic sulphuric acid on the phenyl hydrazone 
of 7-aldehydossobutyric ester : 

CH.-CHj-CHjCOOU 

/C-CH.-CH.-COOE 
-» 0,H,<(5CH +NH, 

The aoid crystallises from water as prisms which 
melt at 134°. 

Indole-3-acetic acid (scatole carboxylic 
^CHj-COOH 
acid) OsHj^ >CH . This substance was 

isolated by E. and H. Salkowski (Ber. 1880, 
13, 2217) from the products of the putrefaction 
of albumen. It has been prepared by EUinger 
(Ber. 1904, 37, 1803) by the action of alcoholic 
sulphuric acid " on the phenyl hydrazone of 
methyl aldehydopropionate 

CHj-CHj-CoSr 
CcH5\^0H 

yC— CHj-CCOR 
-> CeH,<5CH -I-NH3. 

The acid forms small leaflets from a benzene 
solution which melt at 165° and at the same 
time eliminate carbon dioxide, yielding scatole. 

yCCH, 

^ ^CH. This 
NH 



Scatole (3-methylindole) OjHj^ ^ 



substance occurs as a product of the putre- 
faction of albumen and is also formed by the 
fusion of protein substances with potash. It 
was first discovered in human fseoes of which it 
forms the chief volatile constituent (Brieger, 
Ber. 1879, 12, 1986) ; it also occurs in the wood 
of the Celtis cinnamomea (Linol.), Java (Dunstan, 
Chem. Soo. Proo. 46, 21 1 ). It is formed \iath indole 
when the product obtained by reducing indigo 
by means of stannous chloride is distilled with 
zino dust (Baeyer, Ber. 1880, 13, 2339), and can 
be prepared by heating the phenyl hydrazone 
of propionic aldehyde CH,;CHi,CH : NjE-CeHj, 
with an equal weight of zino chloride and dis- 
tilling the product with steam. 

Scatole forms lustrous laminae, melts at 95° 
and boils at 265°-266° (corr.) under 755 mm. 
pressure. It usually has a strong fsecal smell, 
but when pure is stated to be without odour. 
It dissolves in concentrated hydrochloric aoid, 
forming a violet solution. 



134 



INDOLES. 



1-methyl indole O.HjC ;^CH. When methyl 
^N-CH, 
phenyl hydrazone pyruvic acid is treated 
with hydrochloric acid it parts with the elements 
of ammonia yielding 1-methyI indole oarboiylio 
acid 

C,H5-N(CH,).N!0<gg5jj 

JCE yCR 

-> C,H4< ^C-COOH -> ObH/ ^CH 
\N-CH3 \N-0H3 

On heating this compound to 205° it parts with 
carbon dioxide, forming 1-methyl indole (E. 
Fischer and Hess, Ber. 1884, 17, 562). Accord- 
ing to Carrasco and Fadoa (Gazz. chim. ital. 
1007, 37, 11, 49), this substance is also formed 
when dimethyl-o-toluidine is dropped into a tube 
fiUed with reduced nickel heated to 300°-330"'. 

1-methyl indole is a yellow oil which boils 
at 240°-241° (corr.) under 720 mm. pressure. 
It has sp.gr. 1-0707 at 0° and does not solidify 
at —20°. It colours a pine chip moistened with 
hydrochloric acid reddish violet. 

2-Methyl indole CeHj<^g^C.CH,. This 

compound is formed from o-nitrophenylacetone 
by reduction with zinc-dust and ammonia, when 
the o-aminophenylacetone, which is first formed 
in the reaction, eliminates water and passes into 
2-methyl indole (Baeyer and Jackson, Ber. 13, 
187). It can also be formed by heating acetone 
phenyl hydrazone with five times its weight of 
zinc chloride for half an hour on the water bath 
and then for a few minutes at 180° (E. Kscher, 
Annalen, 236, 126). 2-Methyl indole forms 
needles or laminae, melts at 59°-60° and boUs at 
272° (corr.) under 760 mm. pressure. It has a 
smeU resembling that of indole, is sparingly soluble 
in boiling water, but readily dissolves in alcohol 
and in ether. It colours a pine chip moistened 
with hydrochloric acid red. J. ]?. T. 

Tryptophan v. Tryptophan. 

INDONES V. Indeite. 

INOOPHENOLS v. luDAMmES and Indo- 

PHENOLS. 

INDOPyRIN ti. Syuthetio detigs. 

INDOXYL COMPOUNDS. When the hydro- 
gen atom attached to one or other of the two 
carbon atoms present in the five-membered ring 
of indole is replaced by hydroxyl, two isomeric 
compounds may be formed which are repre- 
sented by the two formulae : 

/OH, 



Indoxyl (enol form), 
stable.- 



,/yVoH 

pseudo-Oxindole (enol 
form), labile. 

The presence of the complex CH ; C{OH) in these 
compounds causes them to react in two forms, 
which maybe represented by thefurtherformulae: 






^NH 



u 



NH 



\co 



paeudo-Indox^l (keto form), Oxindole (keto form), 
labile. stable. 

The two modifications are, in these cases, 
tautomeric, that fs to say, only one form can be 
isolated (stable form), but this variety can, 



under certain conditions, yield derivatives of 
the other modification (labile form). 

As shown by the above expressions, the enol 
(or hydroxy) form of indoxyl is the stable variety 
of this substance, whereas the stable form of 
oxindole {g.v.) is represented by the keto 
structure. XJ-OH 

Indoxyl C.Hi^ \(3H. The isolation of 

indoxyl was first effected in the following way. 
It had been noticed from the earliest times that 
under certain conditions human urine deposited 
a blue colouring matter, and the first recorded 
observation of this fact is ascribed by Thudi- 
chum (A Treatise on the Pathology of Urine, 
London, 1877) to Janus Planchus, in the year 
1767. Schunck, in 1857, suggested that the 
chromogen of this blue colouring matter, which 
had previously been identified as indigo by 
Heller and Kletzinski, was the same as indican 
which he had isolated from woad. This was, 
however, disproved by Baumann (Pfluger's 
Arohiv. 13, 291) who, with Brieger (Zeitsch. 
physikal Chem. 1879, 111, 258), isolated the 
chromogen from urine and showed it to be 
indoxyl sulphuric acid. 

Subsequently, Baumann and Tiemann (Ber. 
1880, 13, 415) showed that, like phenol sulphuric 
acid, indoxyl sulphuric acid is decomposed by 
acids into sulphuric acid and a phenolic sub. 
stance — indoxyl — and that this compound it 
quantitatively converted into indigo on oxida- 
tion. Subsequently, the synthesis of indoxyl 
was effected by Baeyer (Ber. 1881, 14, 1741) by 
the following series of reactions. Ethyl o-nitro- 
phenyl propiolate is first converted by shaking 
with concentrated sulphuric acid into ethyl isato- 
genate (molecular rearrangement) : 

yfeCCOOOjHs yCO-C-COOCjH, 

^NOj ^N— 

This substance on reduction yields ethyl 
indoxylate, which is then hydrolysed by caustic 
soda to the sodium salt of indoxylio acid, and 
the free acid from this, when boiled with water, 
is transformed into carbon dioxide and indoxyl. 

' /C(OH) /C(OH) 

CsHX ^C-COOOjHj -> CeHX '^C-COOH 

^NH ^:Sh 

■C(OH) 
^CH. 
-NH 

Indoxyl when pure forms pale yellow crystals 
which melt at 85°, but crystallisation cannot be 
effected in the presence of even slight traces of 
impurities. It dissolves in water, forming a 
fluorescent solution and is readily soluble in 
most organic solvents. It is very unstable and 
readUj^ oxidises when exposed to the air; the 
oxidation to indigo takes place rapidly in alka- 
line solution. It is volatile with steam and 
when treated with isatin in the presence of 
potassium carbonate is converted into indirubin, 
a reaction which may be represented by the 
following equation ; 

CeH,<^|>eH,+OC<JO\NH 
Indoxyl (keto form). 

=C.H.<^g>-C<:^°>NH. 
Indirubin. 



/C(0 

NMTT 



INK. 



136 



/CO-SO,H. 
Indoxyl sulphuric acid CJlA ^GH 

This substance occurs as the potassium salt 
{indicanuria) in human urine as well as in the 
urine' of certain carnivora. It occurs to a con- 
siderable extent in the urine of a dog which has 
been fed on indole. It can be prepared syn- 
tlietically from the potassium compound of 
indoxyl by treatment with potassium pyro- 
sulphate (Baeyer, Ber. 1881, 14, 1744) and also 
by fusing phenylglycine-o-carboxylic acid and 
treating the melt with potassium pyrosulphate 
(Baumann and Thesen, Zeitsch. physikal. Chem. 
1896, 23, 23). The free acid is unstable, but the 
potassium salt forms characteristic glistening 
leaflets from alcohol in which it is sparingly 
soluble. 

/C(OH) 

Indoxylio acid C.H4<r .;^C-COOH, separates 
\NH 
when d. solution of its sodium salt is acidified 
as a white crystalline precipitate which melts 
at 122°- 123° with -vigorous evolution of carbon 
dioxide. J. P. T. 

INDULINES. A very numerous class of 
blue colouring matters belonging or closely 
related to the safranine group of colours. 
They are prepared by heating an aminoazo com- 
pound with an amine in the presence of the 
chloride of the latter. As might be expected, 
such a process allows of an almost infinite series 
of variations, and a great number of the colours 
have at various times been made and used. 

By far the most important is also the earliest 
known ; the details of its preparation, described 
below, are practically those of all the others. 

250 kilos, of aniline are mixed with 24 kilos, 
of hydrochloric acid (35 p.c.) and a solution of 
14-4 kilos, of sodium nitrite is run in. The 
mixture is allowed to remain for some time and 
then heated with steam to 40°-50° in order to 
complete the transformation of the diazoamino- 
benzene into aminoazobenzene. The product 
is then transferred to a cast-iron still capable of 
holding twice the volume of the melt made in it 
and provided with an agitator, swan neck, 
charging hold, thermometer tube and discharge 
valve. 60 kilos, of aniline salt (aniline hydro- 
chloride) are added and the mixture is heated 
gradually so that at the end of about 4 hours the 
temperature of the melt has reached 175°- 180° 
(Schultz, Chemie des Steinkohlentheers, 3rd 
edit. 1901, ii. 343). The mass is now rendered 
alkaline with aqueous sodium hydroxide, the 
excess of aniline distilled oS with a current of 
steam and the residue ground, washed, and 
dried. A medium shade, as produced by this 
method, is known as Indullne 3 B spliit soluble ; 
the formula of its chief constituent is 

Bed shade indulines {e.g. Fast blue R spirit 
soluble) are formed by heating the mixture for 
a short time only and at a lower temperature 
(160°-170°). The bluer shades {e.g. Fast blue 
spirit soluble ; Induline 6 B spirit soluble) are 
obtained by more prolonged heating. 



Much of the induline base prepared in this 
way is sulphonated, but some is dissolved in 
aoetin, Isevulio acid, or ethyltartaric acid, 
forming blue to violet-blue liquors which are 
used for printing (Printing blue, Acetin blue, 
Laevulin blue, &o.). When spirit-soluble indu- 
line is sulphonated it is converted into a sul- 
phonic acid, the sodium salt of which ia soluble 
in water. In this form, various brands of water- 
soluble indulines are placed on the market under 
the names of Induline (various marks), and Fast 
blues, Nigrosine, Coupler's blue. Another series 
of blue to blue-grey or black dyes is produced 
by heating aniline and aniline hydrochloride 
with nitrobenzene or nitrophenol or both in the 
presence of iron borings. Typical processes are 
(a) With nitrobenzene : 175 parts of aniline, 175 
parts of nitrobenzene, 200 parts of hydrochloric 
acid, and 16 parts of iron borings are heated for 
8 hours at 160°-200° until a test portion can be 
drawn out into a thread. The melt is then run 
out into an iron tray and ground. (6) With 
nitrophenol : 100 parts of aniMne hydrochloride, 
60 parts of aniline, 60 parts of nitrophenol, and 
a little iron are heated for 10 hours to 180°. 
(c) With nitrobenzene and nitrophenol : 183 parts 
of aniline hydrochloride, 183 parts of nitro- 
benzene, 137 parts of aniline, 12 parts of crude 
nitrophenol, and 3 parts of iron borings are 
slowly heated for a day, the final temperature 
being about 215°. Towards the end the melt 
must be constantly tested and run out imme- 
diately it begins to thicken, otherwise it will set 
in the pan and then must be chipped out when 
cold. The spirit-soluble nigrosines produced, 
as described above, are sulphonated as in the 
case of the indulines, the products being known 
as Nigrosine soluble. J. 0. C. 

INDURITE V. Explosives. 

INFUSORIAL EARTH v. Kieselouhe. 

INGRAIN BROWN, -ORANGE, -BED, v. 
AzO- COLOUBIIirO mattees. 

INGRAIN COLOURS v. Pwmtjlinb akd ws 

DEETVATIVES. 

INK. A coloured fluid, used in writing, 
printing, &o. (Gr. enghaiiston — engkaio, to burn 
in ; Lat. encaustum, the purple-red ink used 
only in the signature of the emperors; It. 
inchiostro; 'Et.encre; Dutch, inH.) 

It may be a convenient although not rigidly 
accurate division of the subject to recognise 
a distinction between ink prepared for writing 
and that prepared for printing. 

Writing ink. Black vmting ink, as com- 
moidy prepared, ia a ferroso-ferric gallate 
suspended in a solution of gum in water, 
obtained by adding a decoction of substances 
containing tannin (usually nut-galls) to a solu- 
tion of copperas. 

Galls contain gallotannio and gallic acids, 
which, with ferric salts, form a black precipitate ; 
with ferrous salts the precipitate is white, but 
becomes black when oxidised by exposure to air. 
A proportion of gum is added for the purpose 
6t suspending the precipitate equally throughout 
the solution and of preventing its deposit. 

Although other materials may be used, it has 
been found that the best properties of writing 
ink — viz. fluidity, penetration, and permanence 
— are obtained by the use of the ingredients 
above-named. Such inks fall into two main 
classes. 



136 



INK. 



Tannin-iron inks are manufactured from the 
above materials without additions and without 
previous treatment of the materials. The 
following typical recipes are taken from the 
sources named : — 

No. 1 (CJooley's Cyclopsedia). — Aleppo galls, 
well bruised, 4 oz. ; clean soft water 1 quart ; 
macerate in a clean corked bottle for 10 days or 
a fortnight, or even longer, with frequent agita- 
tion ; then add 1| oz. of gum arable dissolved in 
a wineglassful of water and | oz. lump sugar; mix 
well, and afterwards further add -of ferrous sul- 
phate (green copperas), crushed small, 1} oz. ; 
agitate occasionally for 2 or 3 days, when the 
ink may be decanted for use, but is better if 
the whole is left to digest' together for 2 or 3 
weeks. Product : 1 quart of excellent ink, 
writing pale at first, but soon turning intensely 
black. 

No. 2 (Ure).— 12 lbs. of nut-galls, 6 lbs. 
ferrous sulphate, 6 lbs. Senegal gum, 12 gal- 
lons of water. The bruised nut-gaJls are to be 
put into a cylindrical copper of a depth e'qual 
to the diameter, and boiled during 3 hours 
with three-fourths of the above quantity of 
water, taking care to add fresh water to replace 
what is lost by evaporation. The decoction is 
to be emptied into a tub, allowed to settle, and, 
the clear liquid being drawn off, the lees are to 
be drained. The gum is to be dissolved in a 
small quantity of hot water, and the mucilage 
thus formed, being filtered, is added to the clear 
decoction. The ferrous sulphate must likewise 
be separately dissolved and well mixed with the 
above. The colour darkens by degrees in con- 
sequence of the peroxidation of the iron on 
exposing the ink to the action of the air. Pro- 
duct : 12 gallons. 

No. 3 (Lehner, Ink Manufacture, p. 28). 

Ingredients — 

Galls . . . 1200 parts by weight. 
Ferrous sulphate . 800 „ „ 

Gum arable . 800 „ „ 

Water . . . 24,000 „ „ 

Creosote • t ■ 3 „ „ 

Cover the galls with part of the water and 
dissolve the green vitriol, gum, and creosote 
separately in the rest of the water. Poui the 
solution on to the galls, cover up the vessel, and 
allow to stand for 3 weeks, stirring every day. 
The ink will then have reached its full blackness 
and can be bottled for use. 

In other processes the galls are repeatedly 
extracted with boiling water and the extracts 
united and then mixed with the other con- 
stituent's ; or the tannin is extracted from the 
bruised galls with ether and the dry product 
dissolved in water for ink-manufacture. The 
quality of the product seems to be equally good 
whatever method is used, provided the ratio 
between the weights of galls and of ferrous 
sulphate taken is always about 8 : 2. The 
addition of an antiseptic substance such as 
carbolic acid is to be recommended, as the ink 
is thus preserved indefinitely from the attacks 
of mould. 

Gallic acid inks are also made from galls, 
ferrous sulphate, gum, and water, with- the 
difference that the galls are first allowed to 
ferment, whereby the quercotannio acid is con- 
verted into gallic acid. The following is a 
typical recipe : — 



Gall nuts 


60 parts. 


Ferrous sulphate . 


. 10 „ 


Gum . 


. 10 „ 


Water . 


. 2000 „ 


Carbolic acid 


2 „ 



The crushed galls are soaked in the water 
and allowed to ferment. The mass may be 
inoculated with mould from a mouldy piece of 
bread or leather. After 8 to 10 days, boiling 
water is poured on to kill the ferment and the 
liquid drawn o£E and used to dissolve the other 
ingredients. < 

These inks have a fine blue-black colour and 
are not so susceptible to change as the tannin 
inks, but they have fallen into disfavour because 
they must be partially oxidised before use and 
thus take a considerable time to manufacture, 
and even then give a very pale impression on 
paper. Most of the inks now used contain a 
' jiroiiisianal colouring mailer,' the function of 
which is to render the ink easily visible at the 
time of writing and until such time (7-10 days) 
as it shall be completely oxidised to black ferric 
gallate. 

Logwood tannin inks are made by sub- 
stituting logwood chips or logwood extract foe 
part of the galls in a tannin-iiLk recipe, e.g. : — . 
Galls . . ... 36 parts. 
Ferrous sulphate . . 36 „ 
Logwood extract . . 9 „ 
Gum . . . . 36 „ 
Water . . . . 300 „ 
Vinegar . . . , 60 „ 
The method of preparation is sinulai to that 
already described. 

Logwood gallle acid inks are similarly made 
but with preliminary fermentation of the galls. 
These inks have a deep blue-black colour and 
attack steel nibs less than pure tannin inks. 

Alizarin inks are those inks which contain a 
provisional colouring matter other than logwood. 
They contain a sufficient proportion of acid 
(sulphuric or acetic) to keep the iron gallate or 
tannate in solution, and therefore may be pre- 
pared with much less gum than those previously 
described. 

Of the colouring matters used the most 
important is indigo-carmine, which is prepared 
by dissolving dry indigo in fuming sul- 
phuric acid, and after 24 hours neutralising with 
potassium carbonate. The free acid in the 
indigo solution may also be used to dissolve 
metallic iron, thus dispensing with the use of 
green vitrioL 

The following recipe is stated to produce an 
excellent ink : — 



Galls . 


40 parts 


Iron solution . 


. 15 „ 


Indigo-carmine 


5 „ 


Gum 


. 10 „ 


Pyroligneous acid . 


. 10 „ 


Water . 


. 100 „ 



The galls are powdered and soaked in the 
water and half the acid for a week. The iron 
solution is prepared from scrap iron and crude 
pyroligneous acid left together for a ;ireek. 
These solutions are then mixed and the other 
ingredients added. 

At the present time, many other tannin- 
oontaining substances, besides galls, are used in 
the manufacture of inks. It uas been shown 



INK. 



137 



that aumaeh, valonia, and logwood pioduce an 
ink which is indistinguishable from gall-inks 
(Hinrichsen and Kedesdy, J. Soo. Chem, Ind. 
1909, 831), and good inks may be produced from 
(annei's barks (elm, oak, pine, poplar, willow, 
&;c.)> cutch, glim kino, fustic, elder-berries, the 
unripe fruit of the chestnut, walnut, &c. 

In many cases other and cheaper synthetic 
dyes are substituted for the indigo-carmine, but 
this is not nnsessarily detrimental to the quality 
ot the ink. 

Mitchell (Analyst, 1908, 33, 81) has analysed 
a large number of English writing inks and finds 
that, although the composition of any one manu- 
facturer's ink remains fairly constant over long 
periods, there are marked differences between 
the inks of different manufacturers. The total 
solid mattei ranges from 1-89 to 7-94 p.c, the 
ash from 0-42 to 2-52 p.c, and the iron from 
0-18 to 1-09 p.c. 

The age of handwriting can be estimated up 
to the seventh or eighth day, when oxidation is 
complete, but after that no distinction can be 
made until the provisional colour begins to fade, 
usually after about a year. 

It is probable that in oxidised ink the iron 
exists as the tannate 

. (Ci,H,03)3Fe-Fe(C,.H,0,)„ 
described by Wittstein (J. 1848, 28, 221) and by 
Schiff (Annalen, 1875, 175, 176). {See also 
Ozorowitz, Chem. Zentr. 1908, 2, 1024.) 

Biunge prepared a writing fluid, undei the 
name of ' chrome ink,' which was cheap, in- 
tensely coloured, non-corrosive to steel pens, and 
extremely permanent on paper. The manner of 
preparing chrome ink is as follows : 1 part of 
potassium chromate (not dichromate) is added 
to 1000 parts of a saturated solution of logwood 
made by boiling 22 lbs. of logwood in a sufficient 
quantity of water to give 14 gallons of decoction. 
The potassium chromate is introduced gradu- 
ally when the solution is cold, the mixture being 
constantly stirred during the addition. Gum is 
injurious to the mixture. It majy be prepared 
more simply by dissolving 2000 parts of logwood 
extract in a solution of 10 parts of pure potas- 
sium chromate in 100,000 parts of water. 

Ink powders are very little used but can 
easily be made either by cautiously evaporating 
an ordinary ink to dryness and powdering the 
residue, or by mixing the carefully dried and 
powdered ingredients in the proportions used 
f 01 the fluid ink. 

Indelible or safety inks. Compositions i>ass- 
ing under these names consist of finely divided 
carbonaceous substances, such as Indian ink or 
lampblack, held in suspension in a glutinous or 
resinous liquor. They are devised so as to 
resist the action of strong acid or alkaline solu- 
tions. An ink having these properties may be 
made of Indian i& rubbed into ordinary 
writing ink. 

A suspension of lampblack in sodium silicate 
solution makes an excellent safety ink but has 
the disadvantage that it must be kept in air- 
tight bottles. 

Vanadium ink is prepared very simply by 
adding a small proportion of ammonium vana- 
date to a filtered decoction of galls. It is a deep 
black ink, which flows freely from the pen and 
cannot be removed without destruction of the 
paper. 



Copying Ink. Any ink which retains enough 
soIubiUty to give an impression from the 
written sheet on to a sheet of damp paper may 
be used for copying. Bunge's chrome ink de- 
scribed above may be so used. Other logwood 
inks and ferrous gaUate inks being soluble only 
until oxidised by exposure to the air, require the 
addition of some substance which forms a ghize, 
arresting the action of the air. This glaze must 
be soluble when brought into contact with the 
damped copying paper ; the pigment is then 
freed so as to produce the impression. Such sub - 
stances are gum arable, gum Senegal, dextrin, 
and glycerol. Where several copies are re- 
quired, the ink employed should contain more 
staining matter in proportion. 

Hektograph inks are used to give a large 
number of copies, and must therefore contain a 
powerful colouring matter. The original is 
written on ordinary paper with the ink and is 
laid face-down on a sheet of a composition of 
glue and glycerol (about 1 : 6) until the 
ink has been absorbed into the surface of the 
composition. 

By applying sheets of papei with slight 
pressure, 60 to 100 copies can then be obtained. 

A typical ink contains : water-soluble blue 
10 parts, glycerol 10 parts, and water 60-100 
parts. 

Dyes not easily soluble in water ot glycerol 
are first dissolved in alcohol and then mixed 
with the other ingredients. Thus a red hekto- 
graph ink may contain : magenta 20, alcohol 20, 
acetic acid 6, gum 20, and water 40 ; or magenta 
10, alcohol 10, glycerol 10, and water 50. 

Red ink was formerly prepared from Brazil 
wood or extract of Brazil wood, with the addition 
of alum or stannous chloride : e.g. 

(1) Brazil wood, 280 parts; tin-salt, 10 
parts ; gum, 20 parts ; boUed with 3500 parts 
of water and evaporated down until the proper 
depth of colour is attained. 

(2) Extract of Brazil wood, 15 parts ; alum, 
3 parts; tin-salt, 2 parts; tartaric acid, 2 
parts ; water, 120 parts. 

Cochineal ot carmine inks are prepared by 
boiling cochineal in water, precipitating the 
colour with alum and tin salt and dissolving this 
carmine in the requisite amount of strong am- 
monia. Another method is to dissolve 2 parts 
of ammonium carbonate in 200 parts of water 
and macerate for 3-4 hours with 40 parts of 
cooiineal and 2 parts of alum. 

Most of the red inks now used are solutions 
of magenta or eosin in water, together with a 
little gum. Glycerol also is added if the ink 
is to be used for copying. 

Blue ink. Prussian blue is the colouring 
matter commonly employed. The pigment is 
placed in an earthen vessel, and either strong 
hydrochloric acid, nitric acid, ot sulphuric acid 
is added to it. After the mixture has remained 
2 or 3 days, much water is added, and aftet 
settling the supernatant liquoi is drawn ofi from 
the sediment. This sediment is well washed 
until all traces of iron and free acid disappear 
from the water, after which it is dried and mixed 
with oxalic acid in the proportion of 8 parts of 
Prussian blue to 1 part of acid. The pigment 
being now soluble in water, so much of this latter 
is added as will bring it to the required intensity. 

An excellent blue ink can be made by 



138 



INK. 



dissolving 10 parts of indigo-carmine and 5 parts 
of gum in 60-100 parts of water. Solutions of 
blue aniline dyes may be used but are easily 
effaced by bleaching agents and fade on ex- 
posure to light. 

Inks of other colours can be made from de- 
coctions of dyestuffs mixed with alum (used as 
a mordant) and gum Senegal or gum arabic ; as, 
e.g., brown ink fron catechu oi logwood, to 
which a little potassium diohromate is added ; 
violet and purple inks from logwood with a small 
admixture of chloride of tin or of alum ; yellow 
ink from gamboge, &o., &c. Aniline colours 
also oiier a selection of tints for this purpose. 

Gold and silver inks are prepared from gold 
and silver, or from cheaper substitutes such as 
bronze powder and Dutch leaf. The leaf metal 
mixed with honey is carefully ground down to 
the finest possible condition ; it im then well 
washed and dried. A medium is furnished by a 
preparation consisting of 1 part of pure gum 
arabic and 1 part of soluble potash glass in 4 
parts of distilled water. As a rule, 1 part of the 
powder is sufficient for 3 or 4 parts of the 
medium. 

Imitation silver ink is best made by rubbing 
up aluminium foil or powder with gum. 

Sympathetic, Diplomatic, or Secret inks. 
These preparations are devised to trace words or 
figures which are invisible when written but 
which become visible when subjeoted'to heat or 
appropriate chemical reagents. Examples : — ^A 
weak infusion of galls is colourless on paper, 
but becomes black when moistened with a solu- 
tion of copperas; and if a weak solution of 
copperas be used, the writing will be invisible, 
till the paper is moistened with a weak solu- 
tion of galls. Equal parts of copper sul- 
phate and sal ammoniac dissolved in water 
form a colourless ink, the writing of wliich 
turns yellow on the appUoation of heat. Weak 
solutions of silvei nitrate or * of auric chloride 
when exposed to the sunlight become dark 
brown and purple respectively. Solutions of 
cobalt chloride or nitrate give tracings which 
become green or blue when heated and disappear 
again as the paper cools. 

Ink for indiarubber stamps. The following 
preparation produces ink adapted for this pur- 
pose. It does not easily dry upon the pad, and 
is readily taken up by the paper: — Aniline 
colour in solid form (blue, red, &o.), 16 parts ; 
boiling distilled water, 80 parts; glycerol, 7 
parts. The colour is dissolved in the water, 
and the other ingredients are added whilst 
agitating. The ' carbon papers ' used for giving 
two or more copies of written or typed matter 
are coated on one side with a mixture of yellow 
wax and tallow containing a suitable pigment 
such as lampblack or Prussian blue, or some 
aniline colour. 

Ticket-writer's ink is made of good black 
ink, with liquid gum added to produce a gloss. 

Tide tor writing on glass is a solution of gum 
arable in strong hydrofluoric acid coloured with 
some matter which can withstand the acid : 
cudbear is used for this purpose. 

For enamelled cards ordinary printing ink is 
mixed with a few drops of equal parts of copal 
varnish and mastic varnish. 

Utbographie ink ought to conform to the 
following requirements. It should be flowing 



on the pen, not spreading on the stone; 
capable of forming delicate tracings, and very 
black to show its delineations. _ The most 
essential quality of the ink is to sink well into 
the stone, so. as to reproduce the most delicate 
outlines of the drawing and to afEord a great 
many impressions. It must therefore be able 
to resist the acid with which the stone is moist- 
ened in the preparation without letting any of 
its greasy matter escape. 

Lithographic ink may be prepared as fol- 
lows : — ^Mastic (in tears) 8 oz,, shellac 12 oz., 
Venice turpentine, 1 oz. : melt together ; add of 
wax 1 lb,, tallow 6 oz. ; when dissolved, add 
further of hard tallow soap in shavings 6 oz, ; 
and when the whole is perfectly incorporated, 
add of lampblack 4 oz. ; lastly, mix well, cut in 
moulds, and when cold cut it into square pieces. 

Another recipe is as follows : — ^Fuse together 
wax, 18 parts ; soap, 18 parts ; shellac, 14 parts ; 
resin 6 parts ; and tallow, 10 parts. Then stir 
in 2 parts of india-rubber dissolved in 6 parts 
of oil of turpentine, and 6 parts of lampblack. 
The whole is heated till the smell of turpentine 
has nearly disappeared and is then cast into 
sticks. 

Autography is the operation by which a 
writing or a drawing is transferred from papei 
to stone. For autographic ink : — White wax 
8 oz., white soap 2 oz. to 3 oz, ; melt, and 
add lampblack 1 oz. ; mix well, heat strongly, 
and add sheUao 2 oz. ; again heat strongly 
and stir well together. On the mixture cooling 
poui it out as before. With this ink lines 
may be drawn of the finest and fullest class, 
without danger of its spreading ; and the 
copy may be kept for years before being trans- 
ferred. These inks are rubbed down with a 
little water in the same way as Indian ink. 

Printing ink. Ink prepared for use with 
type, copper-plates, &c,, is composed of a 
vehicle and pigment. The chief properties re- 
quired in a good printing ink are : — 

(1) A perfectly uniform syrupy consistency, 

(2) Must be easily transferred from the ink- 
rollers to the type, and from the type to the 
paper. 

(3) Must not smudge types, and must be 
easily washed ofi them with printer's lye. 

(4) The ink must not dry so quickly as to 
set on types or rollers, but must not dry so 
slowly on the paper as to hinder folding, &o,, of 
sheets. 

(5) When dry, the ink must not set ofi from 
the paper on to anything with which it comes in 
contact. 

(6) The printed characters should not show 
a greasy margin. 

(7) The ink should not have a strong smell. 
The ink which most nearly fulfils all these 

requirements is composed of the finest quality 
of lampblack incorporated vrith a pure linseed 
oil varnish. The demand for cheap inks for the 
printing of newspapers and cheap books has 
been met by using cheaper qualities of lamp- 
black and substituting for the varnish various 
compositions of oils and resins with soap, which 
may or may not contain a proportion of linseed 
oU. 

The Unseed oil varnish used for good ink was 
formerly prepared by heating a quantity of 
hnseed oil in a boiler until the vapour evolved 



INK. 



139 



could be ignited. A light was then applied and 
the whole allowed to burn for about half an hour, 
until a trial showed that the oil was of the right 
oonsistenoy. The practice of burning the oil 
gave a dark-coloured product and has now been 
discontinued. 

The present practice is to heat the oil to 
about 380" to |00°, taking every precaution 
to avoid its ignition. The boiler is provided 
with a dosely fitting lid or, better, with a cover 
of wire-gauze, which extinguishes a flame while 
allowing the vapours to escape. 

Provision is made for lifting the boiler from 
the fire or withdrawing the fiie from the boiler, 
or, in some cases, for running off the oil into a 
cold vessel. A gutter round the furnace above 
the fire-door prevents any chance of the oil 
reaching the fire, even should it boil over the 
top of uie pot. In some modem plant the oil is 
heated by means of superheated steam, A varnish 
so prepared is insoluble in water or alcohol, but it 
mingles readily enough with fresh oil and unites 
-with mucilages into a mass diffusible in water 
in an emulsive form. The oil loses from one- 
tenth to one-eighth of its weight by boiling into 
the thick varnish (Watts). 

An average letterpress ink may be made by 
reheating a varnish produced as above and 
adding for each gallon of the original oil 4 lbs. 
resin and 1 lb. brown soap in slices. This is 
then mixed with the requisite quantity of pig- 
ment — rather less than J of its weight in the 
case of lampblack — and the whole thoroughly 
ground and incorporated in a suitable machine, 
usually between rollers of polished granite or 
steel, as in Lehmann's apparatus. The presence 
of soap in the ink causes it to ' lift ' well, i.e. to 
be completely transferred from the type to the 
paper. The following recipes represent vehicles 
of a cheaper class : — 

Linseed oil and resin veihicle. — ^Eesin 50, 
boiled linseed oil 100, resin soap 10, partly boUed 
oil, 6 parts by weight. 

Besin oil vehicle. — Resin oil 60, resin 50, 
boiled linseed oil 60, resin soap 6, thin boiled 
linseed oil 6 parts. 

Cheap mineral oil vehicle, — ^Eesin is dissolved 
in about an equal weight of heated mineral oil 
(petroleum) of sp.gp. 0-880-0-920 (Wass, Fr. 
Pat. 322298, 1908). 

Composition vehicles. 6 kilos. Venice turpen- 
tine, 16 kilos, castor oil, and 1 kilo, white wax, 
mixed at 100° (Knecht). 9 kilos, thick turpen- 
tine, 10 Idles, soft soap, and i kilos, oleine, 
mixed hot (Rijd). 

The lampblack used is of various qualities 
according to the price of the ink. The propor- 
tion used is just sufficient to give a full black 
impression, and this is less with the better 
qualities of lampblack. The ink for rotary 
machines contains about 28 p.o. of lampblack, 
that for high-speed newspaper printing about 
24 p.c, that for book-printing about 21 p.c, and 
and that for illustration work about 19 p.o. 
with 2 p.c. of Prussian blue and 1 p.c. of indigo. 
Brackenbusch's inks consist of 26 parts 
paraffin oil, 45 parts of fine colophony, and 
15 parts of lampblack. The amount of colo- 
phony is reduced in soft inks for high-speed 
HTOrk. 

It has been proposed to use oxides of iron or 
manganese as black pigments for printing inks. 



in which case the paper could be bleached and 
subsequently re-made into white paper. This 
cannot be done with the lamp-black inks now 
used (see e.g. Fireman, U.S. Pat. 802928, 
1905). 

It is said that so marvellously thin is the 
layer of ink on small type that one pound weight 
even of cheap newspaper ink will cover no less 
than 7000 square feet of type matter. 

Coloured printing inks. These inks are 
made from the varnishes above described by the 
addition of dry colours, taking great care that 
the colours are thoroughly well ground and 
assimilated with the varnish, since lumps of 
any kind not only olog the type but alter the 
tint. Some tints which are exceedingly light 
will require an admixture of white powder to 
give the necessary body to the ink. 

The following pigments are eligible for in- 
corporation in printing inks : — 

White. — Heavy spar (barium sulphate) and 
zinc white. 

Bed. — Orange lead, vermilion, burnt sienna, 
Venetian red, Indian red, lake vermilion, orange 
mineral, rose pink, and rose lead. 

Yellow. — Yellow ochre, gamboge, and lead 
chromate. 

Blue. — Cobalt, Prussian blue, indigo, Ant- 
werp blue, Chinese blue, French ultramarine, 
and German ultramarine. 

Oreen. — Usually mixtures of yellow and blue, 
but sometimes chrome green, cobalt green, 
emerald green, or terre verte. 

Purple. — ^A mixture of those used for red 
and blue. 

Deep brown. — Burnt umber with a little 
scarlet lake. 

Pale hrown. — Burnt sienna ; a rich shade is 
obtained by using a little scarlet lake. 

Lilac. — Cobalt blue with a little carmine 
added. 

Pale lilac. — Carmine with a, little cobalt 
blue. 

Aniber. — Pale chrome with a little carmine. 
Pink. — Carmine or crimson lake. 
Shades and tints. — A bright red is best got 
from pale vermilion with a little carmine added ; 
dark vermilion when mixed with the varnish 
produces a dull colour. Orange red and ver- 
milion ground together also produce a very 
bright tint, and one that is more permanent 
than an entire vermilion colour. Cheaper sub- 
stitutes are orange mineral, rose pink, and red 
lead. Lead chromate makes the brightest 
colour. For dull yellow, use yellow ochre. In- 
digo is excessively dark, and requires a good deal 
of trouble to lighten it. It makes a fine showy 
colour when brightness is not required. Prussian 
blue is useful, but it dries very quickly, hence 
the roller must be frequently cleaned. The 
objection to Prussian, Antwerp, and Chinese 
blues, is that they are hard to grind and likely to 
turn greenish with the varnish when used thin. 
For green any of the yellows and blues may be 
mixed. The varnish itself having a yellow 
tinge will produce a decidedly greenish tmt with 
a small quantity of Antwerp blue. Emerald 
green is got by mixing pale chrome with a little 
Chinese blue, and then adding the mixture to 
the varnish until the tint is satisfactory. 

In using painter's colours it is advisable to 
avoid as much as possible the heavy ones. Some 



uo 



INK. 



colours require less oil in the varnish than 
others. Foe the comparative permanence of 
colouring matters, v. Piombnts. 

A bronze of changeable hue may be given to 
inks with the following mixture (Southward) : — 
Gum sheUac IJ lbs. dissolved in one gallon of 
0-9S p.c. ajcohol or Cologne spirits for 24 hours. 
Then add 14 oz. aniline red. Let the mixture 
stand for a few hours longer, when it will be 
ready for use. When added to good blue, black, 
or other dark ink, it gives a rich hue to it. The 
quantity must be carefully apportioned. 

Bronzing, the production of printed matter 
having the colour and lustre of gold or silver, is 
carried out by printing with a varnish which 
remains ' tac%' ' for a time, and then dusting 
over the whole surface with bronze powder oi 
aluminium powder or similar substances. The 
powder adheres only to the varnish and thus 
produces the desired eSect. 

Such a varnish may be produced by melting 
into a good linseed oil varnish sufficient bees- 
wax to give it the consistency of lard or tallow. 
{See Ure's Diet, of Arts, Manufactures, &c. ; 
C!ooley's Cyclop, of Practical Receipts ; Lehner's 
Ink Manufacture ; Southward's Practical Print- 
ing; Noble's Principles and Practice of Colour 
Printing; L. E. Andes' Oil Colours and Printer's 
Inks; and Seymour's Modem Printing Inks.) 

niEANI FAT. A fat obtained from the 
seeds, of the East African tallow tree, Stearoden- 
dron StvMmannii (EngL). 

INOSIC ACID, INOSINE v. 'Cashine. 

INOSITOL (Inoaite). A number of natural 
substances having the composition of cyclic 
polyalcohols, e.g. hexahydroxyc^cZohexanes 
CeH,(OH)e, are often classed with the carbo- 
hydrates since they have the same formula, 
taste sweet, occur along with them in nature, and 
possibly have been formed from them by the 
junction of the ends of the six carbon chain, 
although such transformation has never been 
realised in the laboratory. Typical of the class 
is inositol. No less than nine stereoisomeric 
inositols : 

(OH)CH<«^j§iHgi!>CH(OH) 

are possible, of which seven are inactive and 
two optically active and enantiomorphio. Kve 
of these have been described, viz. optically 
active (2- and {-inositol, and inactive inositol, 
cocositol and scyUitol, Similar pentahydroxy- 
c^cZohexanes are likewise found in plants. 
These are .(2- and 2-quercitol. 

The formation of furfural on distillation of 
tne«oinositol with phosphoric anhydride in a 
copper vessel (Neuberg, Biochem. Zeitsch. 1908, 
9, 551) is the only instance in which a complex 
substance has been obtained common to both 
the carbohydrates and inositol. 

d-Inositol (maiezodarnbosa) is prepared by 
demethylation (boiling with concentrated hy- 
driodic acid) of the naturally occurring methyl 
ether, pinltol. It crystallises in anhydrous 
prisms, nLp. 247°-248°, [a]jj4-65° without 
mutarotation and forms hexacetyl and hexa- 
benzoyl derivatives. 

Pinltol {pinite) CjHuOe, also called matezUe 
and eennite was discovered in the resin of the 
CalifornianPt»i'!wZo?»6eriia?io(Dougl.)(Berfchelot, 
Compt. rend. 1856, 41, 392). It occurs in the 



residues of the manufacture of conif erin, in senna 
leaves, and in the liana of Madagascar rubber 
{mateza roritina). It crystallises in colourless 
rhombs, m.p. 186° [a]i,-f 65-5°. The structure 
of pinitol was established by Maquenne (Compt 
rend. 1889, 109, 812). 

Mnositol was obtained by Tanret (Compt. 
rend. 1889, 109, 908) by demethylation ol 
quebrachitol. It crystallises in needles; m.p. 
247° [o]o-65°. 

Quebrachitol (quehrachite) occurs in que- 
bracho bark. It crystallises in prisms; m.p. 
186° [a]i,-80°. 

r-lnositol, obtained by mixing the d- and ' 
Msomerides in equal quantities, is optically 
inactive, m.p. 253°. Tanret {Compt. rend. 1907, 
14S, 1196) has obtained both racemic- andmeso- 
inositol from fresh ripe berries of mistletoe. 

Meso- OT t-Inositol {damtose, nvcile) is 
widely distributed in both plants and animals. It 
occurs in muscles, in the heart, lungs, and liver, 
in beef and horse flesh, and in the urine in cases 
of Bright's disease. In plants, it is found in 
beans, peas, &c., in the leaves of asparagus, 
oak, ash, walnut, &c., in all parts of the grape 
vine and hence in wines and in fungi. The 
chief source is the leaves of the walnut tree 
(Tanret and Villiers, Compt. rend. 1877, 84, 393 ; 
1878, 86, 486), but very much larger quantities 
are afforded by mistletoe. It may also be 
prepared from cochineal mother liquors. It 
crystallises in bunches of needles, m.p. 225°, and 
does not reduce Fehling's solution. Yeast is 
without action, but certain fungi decompose it. 
The hexacetate forms monoclinic plates, m.p. 
212°. Hugo Muller (Chem. Soc. Trans. 1907, 
91, 1780) has described and measured the crystals 
of the monobromopentacetate, minute crystals, 
m.p. 240°, the dibromot«tracetate broad trans- 
parent prisms, m.p. 140°, and scaly crystals, 
m.p. 235° ; also of inositoldibromohydrin, m.p. 
210°. 

When inositol is evaporated with nitric acid 
almost to dryness and then again carefully 
evaporated with ammoniacal calcium chloride, 
a rose red colouration is obtained which enables 
0-0005 gram to be detected with certainty 
(Scherer, Annalen, 1850, 73, 322). With 
ammoniacal strontium acetate, a still more 
delicate violet colouration is obtained. 

Bomesitol, the monomethyl ether, occurs io 
Borneo rubber : it forms rhombic prisms, m.p. 
199°-203°. 

Dambonitol, the dimethyl ether, is found in 
Gabon rubber : it crystallises in hexagonal 
prisms, m.p. 195°. 

Phytin, which is present in many jdant seeds 
and has been isolated from rice bran, is inositol 
phosphoric acid (Winterstein, Zeitsch. physiol. 
Chem. 1908, 58, 118). 

Cocositol (cocosite) CsHjjO,, was discovered 
by Hugo Miillei in the leaves of Cocoi nucijera 
(linn.) and Cocoa plumoaa (Hook.) (Chem. Soc, 
Trans. 1907, 91, 1767). It crystallises from watei 
in large transparent lustrous monoclinic crystals, 
m.p. about 345°-350°, and is optically inactive 
It forms a hexacetate, giving prismatic crystals, 
m.p._ about 300°, also a benzoate and nitrate. 
It gives the red colouration characteristic of 
inositol (Soherer'e reaction). H. Miiller (private 
communication) regards it as identical with 



INVERTASE. 



141 



scyllitol : the ooourrenoe of this substance in 
two Buoh different organisma as the cocoa-nut 
palm and the dog-fish is most lemaikable. 

ScylUtol (aoyUite) CsH.jOj, disooTcred by 
Staedeler and Friedriohs (J. pr. Chem. 1858, (L) 
73, 48) in various organs of the Plagiostomi 
(dog-fish) has been investigated by J. MiiJxer. 
It is inactive, crystallises in hard lustrous mono- 
clinic prisms, m.p. above 339° and is sparingly 
soluble in water. It gives Scherer's reaction 
and forms a hexacetyl derivative. 

(f-Quereitol CsHj^Oe is found in the acorn 
and in minute quantity in the cork and bark of 
the oak. Hugo Miiller (Chem. Soc. Trans. 1907, 
91, 1766) has also obtained it from the leaves of 
Chamceropa humilis (Linn.), the only Eurpoean 
representative of the palm family, which was 
formerly used like esparto tov making paper. 
Theleaves contain I'SSp.c. of queroitol. They.are 
crushed, extracted with boiling water, and the 
extract precipitated first with neutral and then 
with basic lead acetate. The lead in solution is 
removed and the filtrate evaporated until 
crystals appear. It crystallises in prisms, m.p. 
234° [o]j,+20-16°. It is not fermentable and 
forms acetyl and similar esters, showing that it 
contains five hydroxyl groups. Potassium 
permanganate oxidises it to m^onic acid and 
other products, confirming the structural for- 

mula as CH<™j8gjgggi}>CH(0H). 

Z-Qaercitol was obtained by Power and Tatin 
(Chem. Soc. Trans. 1904, 85, 624) from the leaves of 
Gymnemasylvestrei'R.'Bi.). It crystallises in prisms 
from water or needles from alcohol, m.p. 174° 
[ol„— 73-9°, and forma penta-aoetyl and peuta- 
benzoyl derivatives. On oxidation with potas- 
sium permanganate, malonic acid is formed; with 
sodium hypobromite, the product is diketotri- 
hydroxyhexahydrobenzene CjH502(OH)3. It is 
not the optical antipode of d-quercitol. 

Quercitol contains 4 asymmetric groupings 
and therefore 8 optically active and two un- 
resolvable inactive modifications are possible. 

E. E, A. 

INSECTICIDES v. Plaint-sprats. 

INSECT WAX V. Waxes. 

INTENSIFIERS v. Photogeaphy. 

INULA CAMPHOR v. Camphobs. 

INULIN V. Cabboeydbates. 

INVERTASE {Sricrase). Invertase is the 
enzyme which hydrolyses or inverts sucrose to 
dextrose and Isvulose. It is present in all 
yeasts except 8. octosporus, 8. capsvlaris, and 
' <Sf. membranafaeiena (Hans.), and is extremely 
active. According to O'Suuivan and Thomson 
(Chem. Soc. Trans. 1890, 57, 834), whose 
contribution to the subject is still a classic, 
it can hydrolyse 200,000 times its weight of 
sucrose, and probably this figure is much under- 
stated, as is the case with other enzymes, but 
little is known of its nature. 

O'SuUivan purified invertase by fractional 
precipitation so long as it remained active, and 
found that the proportion of carbohydrate 
increased. He identified this as mannose, as 
was also done by KoeUe (Zeitsoh. physiol. Chem. 
1900, 29, 429). A very pure preparation was 
obtained by Osborne {aid. 1899, 28, 399) which 
gave none of the protein reactions, except 
precipitation by copper sulphate, lead acetate, 
and phosphotungstio acid ; it gave the biuret. 



xanthoprotein, and Millon's test faintly, and 
could not be freed completely from carbo- 
hydrate. It also always contained nitrogen 
and ash. Salkowski (Zeitsch. physiol. Chem. 
1909, 61, 124) considers that invertase does not 
contain carbohydrates and that the yeast gum 
which accompanies it is an impurity. 

According to Mathews' and Glenn (Bio- 
Chem. J. 1911, 9, 29), the most active prepara- 
tion contains about 2 p.o. of ash and 2-2 p.c. of 
nitrogen. It consists of a gum and a nitro- 
genous portion yielding 70-76 p.o. of mannose 
on hydrolysis. These authors consider invertase 
to consist of a union of an inactive colloidal 
gum with an active protein ferment : by the 
action of acid, the ferment is freed from the 
carrier and rendered active. 

Invertase appears to be effective in all cases 
where dextrose and Isevulose are united, even 
when a third sugar molecule is attached to these. 
Thusithydrolysesra£&nose,gentianose,melicitose, 
and etachyose, splitting ofE lasvulose in each case. 

Invertase is of common occurrence in the 
vegetable kingdom : it is present in buds, 
flowers, and leaves of the higher plants and in 
numerous mould fungi. It is not so widespread 
in the animal body as maltase, being practically 
limited to the mucous membranes of the ali- 
mentary canal. 

The laws regulating the velocity of invertase 
action are dealt with elsewhere (v. Fbembnta- 
TiON and Hydkolysis). 

It is very sensitive to the minutest quantities 
of alkali, which retards or stops its action, and for 
this reason its action is accelerated by dilute 
acids or acid salts, although probably, like 
diastase, it is most active in truly neutral solu- 
tion. Quantitative work with invertase must 
be carried out in hard glass vessels and with 
solutions which have been stored and measured 
in such vessels. It is the neglect to avoid alka- 
line impurity which has occasioned many of the 
controversitd statements in the extensive litera-, 
ture relating to this subject. 

The rate of action is much influenced by 
temperature : SS'-OO" being that of maximum 
activity, beyond which it becomes weakened by 
heat (see also papers by Euler, Zeitsch. physiol. 
Chem. 1910 and 1911). It is destroyed between 
65° and 70°. The power of the enzyme to resist 
heat is considerably increased by the presence 
of sucrose : according to O'SuUivan, it will 
withstand a temperature 25° higher. 

An active solution of invertase is readily 
obtained by extracting dried yeast with water 
or by shaKng up living yeast with chloroform 
water. A very active permanent preparation 
may be prepared by setting aside washed 
pressed yeast with a little water to autolyse at 
37° for a few days. The liquid is filtered and 
alcohol added a few cub. cm. at a time to the 
filtrate so as to keep the precipitate in a granular 
form. The liquid is decanted, the precipitate 
washed first with a little 60 p.o. and then with 
80 p.c. alcohol and at once dissolved in a minimum 
quantity of water. The precipitation process 
may be repeated and the final product dissolved 
clear in the smallest quantity of water and 
bottled with a little toluene. This solution, 
wMch is of very high activity, may be kept for 
years without its aotiTity materially changing 
(«. Ebbmbntatioh). E. E. A. 



lODALBACID, lODALBIN, lODANISOL, lODEIGONS. 



U2 



lODALBACID, lODALBIN, lODANISOL, 
lODEIGONS, ». Synthbtio dbtjos. 

lODEMBOLITE v. CnBAiiaYKiiE. 

lODGLIDIN, lODDJ, v. Synthetio drtjqs. 

IODINE. Symbol I. At.wt. 126-92. This 
element was discovered in 1812 by Courtois in 
the mother liquor of kelp. The discovery was 
first announced to the French Institute in 1813. 
The properties of the new element were further 
investigated by Clement and Desormes, Gay- 
Lussac, and Davy. 

Iodine is a crystaUine solid of greyish-black 
colour and bright metallic lustre resembling 
plumbago. Its sp.gr. is 4-948. It is obtained 
by sublimation in brilliant rhomboidal plates, or 
in elongated octahedrons belonging to the tri- 
metric system. In very thin plates it transmits 
light of a red colour. It melts at 114-15°, and 
boils at 184-35° (Bamsay). It volatilises at 
ordinary temperatures spontaneously in the air, 
diffusing an odour resembling chlorine. It is 
sometimes employed in this way in hospitals as 
a disinfectant. The vapour has an intense rich 
violet colour, and is one of the heaviest of all 
known gases, having a sp.gr. of 8 -801. A stratum 
4 inches thick presents a black mass quite im- 
pervious to light. It is very slightly soluble in 
water, requiring about 7000 parts for solution. 
It is soluble in chloroform, bromoform, carbon 
disolphide, light petroleum, and benzene, form- 
ing violet solutions ; also in ethyl, methyl, and 
amyl alcohols, and in ether and glycerol, forming 
brown solutions. It is very soluble in potas- 
sium iodide, of which 1 part in 2 parts of 
water wUl dissolve 2 parts of iodine. In re- 
actions it resembles chlorine and bromine, but 
is less energetic, and is displaced by these 
elements from its compounds with hydrogen and 
the metals. It has a strong affinity for most of 
the metals, and in the presence of water, attacks 
and dissolves gold. The most characteristic re- 
action of free iodine is the dark blue compound 
formed with starch; this test is ertremely 
sensitive, and will reveal the presence of one- 
miUionth part in any liquid containing it. 
Another characteristic reaction is to liberate the 
iodine from a solution by nitrosulphurio acid, 
and dissolve it out by carbon disulphide : this 
affords an accurate and easy method of esti- 
mating it by the depth of the crimson colour of 
the solution ; it is sAbo extremely sensitive, and 
well adapted to estimate small quantities of the 
element. 

Iodine in minute quantities is very largely 
distributed throughout the animal, vegetable, 
and mineral kingdoms. As a mineral it occurs 
in combination with silver, mercury, and lead, 
in ores from Mexico, Chile, and Spain, with 
zinc in Silesia, and with lead in South America. 
It is also found in dolomite from Saxony, 
in limestone from Montpellier, in shale from 
Sweden, and in calcium phosphate from France. 
It exists also in the ' caliche ' of Chile in the 
form of sodium iodate. This is the only mineral 
source from which it is manufactured, and has 
been for many years the most important of all 
the commercial sources. 

Many mineral waters contain iodine, notably 
those of Carlsbad in Bavaria, HaU in Austria, 
Marienbad in Bohemia, Holberg in Fomerania, 
Halle in Saxony, Sales in Piedmont, Nix in 
Savoy, Kreuznach in Galicia, Halse in Java, 



and JaUien in France. It is also found in the 
waters of Friedrichshall, Castellamare, Heilbrun, 
Eomburg, Seidchutz, and Vichy; and in this 
country in those of Leamington, Bonington, Bath, 
Cheltenham, and Woodhall. It is a valuable 
remedy ia skin diseases. The sea is an abun- 
dant source of it. Iodine is always present in 
sea-water, but in such a very minute proportion 
that it is difficult of detection except by operat- 
ing on large quantities. It has been estimated 
in the Atlantic at I part in 280,000,000 (Stan- 
ford) ; all fishes and all animal products from 
the sea appear to contain iodine, but in very 
minute quantity. The following table shows a 
few of the marine products in which it has been 
estimated : — 



Cod -liver oil 


0-000322 p. 


3. iodine. 


Cod-livei . 


0-000817 




Codfish . 


0-000160 


^^ 


Herririg, salt 


0-000650 


j_ 


Whale oil . 


0-000100 


j^ 


Seal oil . 


0-000050 


,j 


Oysters (Portuguese) . 


0-000040 


jj 


Prawns 


0-000440 




Limpets . 


0-003200 


"^ 


Cockles . 


0-002140 




Whelks . 


0-008920 




Mussels 


0-035720 




Sponge (Turkey) 


0-200000 


,, 


Sponge (Honeycomb) . 


0-054000 


„ 



Nearly all seaweeds or marine algse contain it. 
It is present even in the Zostera marina (L.) or 
grass wrack, natural order NaiadacecB, a flower- 
ing plant growing only in the sea ; but there are 
some remarkable exceptions. The gelatinous 
species of algee, the Ohondrus erispus (L.) (or Irish 
moss), and Oelidium comewm (Lam.) of British 
species, and the Eucheuma spinoaum [(L.) J.Ag.], 
or Agar agar of foreign species, do not contain 
iodine. The Enteromorpha compressa [(L.) Gre v.], 
or common sea grass, when dry has a strong 
odour of the sea, but does not contain iodine. 
The salsola or salt wort, Salsola Kali (L.), 
natural order ChenopodiacecBf growing on the 
seashore, and from which barilla was made, con- 
tains no iodine. Some of the algse are compara- 
tively rich in iodine, and the ash of these plants, 
known as kelp, for many years formed the only 
commercial source of this important element. 

Manufacture. — By far the greater bulk of all 
the iodine produced is now extracted from the 
mother liquors of the ititrate works in Chile, but 
the mamSacture of iodine from kelp has for 
long been carried on in Scotland and in France, 
and within recent years has been started in 
Korway and in Japan. Courtois, a saltpetre 
maker in Paris, who discovered io^ne, obtained 
it from the kelp liquors which were used to 
furnish the salts of potash required in his manu- 
facture, and this was for many years the only 
commercial source of iodine. The manufacture 
was unsuccessful commercially in the hands of 
the discoverer, and he died in poverty. It was 
afterwards successfully carried out by MM. 
Coumerie, of Cherbourg, and has continued to be 
an important manufacture on the Normandy 
coasts. In this countnr it was first made on the 
small scale by Dr. Ure of Glasgow, and the 
manufacture has since been almost exclusively 
confined to that city, where it has assumed con- 
siderable importance. It was first made there in 



IODINE. 



143 



quantity in 1841, and the imports of kelp into the 
Clyde in that year amounted to 2,665 tons. In 
1846, there were four small works engaged in the 
manufacture of iodine. Kelp was then used for 
soap making on account of the sodium carbonate 
it contained, and the iodine was extracted from 
the lyes of the soapboilers. In 1846 there were 
twenty makers of iodine in Glasgow, who then 
treated the kelp directly, extracting also the 
potash salts which had a high value in the market. 
The fall in the price of potash salts owing to the 
discovery of the Stassfurt mineral, wmoh re- 
duced the price to one-third, the very variable 
character of the kelp used, and the extreme 
fluctuations in the price of iodine, ranging from 
is. to 348. per lb., soon reduced the number of 
makers, and now there are only three works in 
Scotland. The produce of iodine from kelp was 
so limited that it offered unusual temptations to 
speculators, who derived most of the benefit 
from the high prices, the manufacturers suffering 
the losses during the low prices. 

The history of kelp, or varec as it is called in 
France, is extremely interesting. It is a crude 
rough slag made by burning seaweed in long 
shallow pits. For many years it was a large and 
valuable article of commerce, and greatly en- 
riched the proprietors of the West Highland 
estates where it was principally mSide. It was 
then the only source of soda. At the beginning 
of last century it realised 202. to 221. per ton, 
and the Hebrides alone yielded 20,000 tons per 
annum, worth upwards of 400,0002. ; and as the 
burners only received 35«. to 40s. per ton for 
their share, the profit to the Highland lairds was 
enormous, and it induced an amount of extrava- 
gance which ruined most of them. It was 
largely used in soap making and in glass making, 
and within the last hundred years there were 
glass works at Dumbarton using this material, 
which were celebrated for the quality of their 
glass. At a glass works in Drontheim in Norway, 
it was still used for this purpose up to about 
forty years ago. The importation of barilla 
gave the first blow to kelp, and it fell in price, 
and for the twenty-two years ending 1822, the 
average price was 102. I0». The duty was then 
taken off barilla, and the price of kelp again fell 
to 82. 10*. ; in 1823, the salt duty was repealed 
and kelp fell again to 32., and in 1831 to 22., at 
which price there was no further profit on the 
manufacture. In the meantime soda was being 
largely made by the vLeblanc process, and kelp 
was superseded altogether as a source of soda. 
It must have been a most expensive source, as 
it yielded only about 4 p.c. of alkali and often 
less than 1 p.c. ; and at one time must have cost 
the soap makers what would have been equal to 
1002. per ton foi soda ash, worth now about 
62. 10s. 

The manufacture of iodine and potash salts 
then began'to assume some importance, but the 
kelp required was not the same, that which 
contained the most soda containing the least 
potash and iodine. Moreover the kelpers had 
been taught to burn at a high temperature, which 
improves the yield of sodium carbonate but 
volatilises much of the potash and some of 
the iodine. The seaweed employed by the 
kelpers was of a kind containing little iodine, 
and not very rich in potash. They used almost 
exclusively the black wrack, cut in large quanti- 



ties in the Highland lochs, and consisting of the 
three fuci, Fticus vesiculosus (L.), Aseophyttum 
nodosum (Le Jol.), and F. serratus (L.), which 
are all uncovered at low tide. This is now 
entirely unutilised ! the kelp made from it was 
known as eut-weed kdp. The following is the 
average analysis from numerous cargoes of the 
kelp : 

Potassium sulphate . . 23-08 
Potassium chloride . . 1 -45 
Sodium chloride . . . 19-13 
Sodium carbonate . . . 6-48 
Insoluble . . . .43-71 
Water 6-22 



Total potash, KjO . 
Iodine, lbs. per ton , 



100-07 
. 13-40 
. 4-18 

=0-18 p.c. 

Drift kdp is the only variety now employed as 
a source of iodine. It is made from the red wracl^, 
the Laminaria digitata [{L. ) Lamx.],or tangle, and 
the L. slenophyUa, which are always submerged 
by the tide, and contain about ten times as much 
iodine as the fuci. These seaweeds are torn up 
by the storms from the rooks on which they 
grow, and cast ashore ; unlike the black wrack, 
these plants suffer much from rain, the more 
valuable salts being completely washed away, 
and are often after drying quite valueless, the 
kelper losing all his labour. From the time of 
its discovery, the iodine was the most important 
product, but the potash salts were also very 
remunerative at first. Potassium chloride, or 
' muriate,' as it is technically called, was worth 
252. per ton. The discovery of the Stassfurt 
mineral reduced its value to about one-third, 
and the further discovery of bromine in the same 
mineral reduced the price of that element from 
384. to Is. 3(2. per lb., the present value. The 
amount of bromine in kelp is small, only about 
one-tenth of the iodine, and it has not been 
extracted from this source for the last forty 
years. It is remarkable that the algra should 
select iodine, as bromine is a much larger con- 
stituent of sea-water, which usually contains 
about 6 parts in 100,000, and according to 
Dittmar appears to bear the constant relation to 
the chlorine of 0-34 to 100, whereas iodine exists 
only as a minute trace, difficult even of detection, 
although the aggregate amount in the ocean 
must be enormous. 

The algse differ considerably in the propor- 
tion of iodine which they take up from the sea- 
water, and only two species, the Laminaria 
digitata, and the L. etenophylla are worth burn- 
ing for kelp. 

It is remarkable that the giant algse of the 
Falkland Islands contain very little iodine, 
although these are the largest sea-plants in the 
world. The DuviUcea utilis (Bory.), a marine tree 
with a stem a foot in dia&eter, and the Macro- 
cystis pyrifera (Turn.) which grows to the length of 
1500 feet, contain only traces of iodine ; in some 
samples it can scarcely be detected. 

The following table shows the average yield 
of the most important varieties. The kelp plant 
figures are taken from a large number of analyses, 
from seaweed gathered all around the shores of 
Great Britain and Ireland j also Denmark, Nor-, 
way, and Iceland. 



144 



IODINE. 



Dry weeds 


Per 
cept. 


Ibs.pex 
ton. 


Drift Kelp: 






liomuuma digitata [(L.) Lamx.], 






Tangle, stem 


0-4635 


10-158 


„ etenophyUa 


0-4777 


10-702 


„ taccharina (Lamx.}, Sugar 






Wrack 


0-2794 


6-268 


Fmat serratut (LX Black Wrack . 
Aicophyllum nodosum (Le Jol.). 


0-0856 


1-807 






JKnobbed wrack 


0-0572 


1-281 


Fueui veaculoBos (L.), Bladder Wrack 


00297 


0-665 


Various : 






Halidryt nOquosa [(L.) Lyngb.], Sea 






Oak 


0-2131 


4"773 


Japanese Seawied, edible 
nvmanOuiMa lofea [(L.) Lyngb.], Sea 


0-3171 


7-102 






L^ces 


0-0892 


1-998 


Shodj/menia palmata [(L.) Grev.], 






Dulse, edible .... 


0-0712 


1-594 


Chorda Fitim [(l.) Stackh.], Sea 






Twine 


0-1200 


2-688 


ZoBtera marina (L.), Grass Wrack . 


0-0457 


1-023 


jDuviOcea vHUs (Borg.), Falkland 






Islands 


0-0075 


0-179 


MacroeystU pyr^era (Turn.), Talk- 








0-0308 


0-690 



The seaweeds chiefly used in Japan for the 
extraction of iodine are Laminaria, ap. Ecklonia 
cava, E. bicyclia (Kjellm.), and Sargassum sp. The 
iodine content varies with the age of the algee and 
also -with the time of year, being greatest during 
June to September ; the following figures give 
the iodine content of some of the raw seaweeds : 
Ecklonia cava, 0-23 p.c. ; E. bicyclis, 0-27 p.c. ; 
Sargassum ap., 0-05 p.c. ; Laminaria anguatata, 
(Kjellm.), 0-13 p.c. ; L. Umgiaaima, 0-17 p.c. ; L. 
ochotensia, 0-19 p.c. 

It will be seen that even in the drift weeds 
the quantity of iodine is inconsiderable, but if 
the plants are properly burnt to a loose ash at 
a low temperature, they ought to yield a kelp 
containing 25 to 30 lbs. of iodine to the ton; 
12 lbs. per ton is, however, above the average 
yield from ordinary drift kelp. The kelpers 
often neglect to protect the seaweed from the 
action of rain, which washes out the soluble 
iodides, and moreover it is difficult to prevent 
them from burning it into a hard slag by working 
it up, when molten, -with iron clauts. Sand and 
stones are thus mixed up -with it, and the great 
heat employed drives oS some of the iodine. 
The result is a hard slag of great density, and 
this density forms one of the difficulties in in- 
ducing the kelpers to burn the weed to a loose 
ash, which they imagine, from the lightness, 
wiU not give them the weight they expect. As 
an actual fact, of course, the total weight of the 
ash so produced is considerably more, from the 
same quantity of weed used ; but old faUaeies 
die hard, especially amongst the poor and 
ignorant people who do this work. There is 
tiie further disadvantage that the sulphates are 
reduced to sulphides or oxysulphides, and a con- 
siderable extra expenditure oi oil of vitriol to 
decompose these is entailed; sulphur is thus 
obtained as one of the by-products of the lixi- 
viation of kelp, in which it ought not to exist 
u,t aU. The presence of silica as sand greatly 
assists the volatilisation of the iodine. 

The table at top of next column shows the 
analyses of very good samples of Irish and 
Scotch kelp, and ^o of the latter burnt into 
loose ash, and the comparison of these indi- 
cates clearly the effect of the heat of burning. 

A different method- of manufacture was 







■j 


Kelp 


Ash 




Irish 


Scotch 


Scotch 


Potassium sulphate 

„ ch oride 

Sodium „ . 

„ carbonate . 

„ sulphide . 

„ thiosulphate 
„ iodide 

„ thiocyanate 

Soluble organic matter 

Insoluble 

Water . 


11-14 

27-17 

9-00 

6-82 

Heavy 

trace 
1-22 
0-82 
Heavy 

trace 
Nil 

41-41 
3-10 


13-95 
17-79 
14-00 

3-92 

Heavy 

trace 

0-75 

0-76 

Heavy 

trace 

Nil 
44-80 

4-05 


12-71 

1809 

6-80 

3-43 

Slight 
trace 

0-17 

1-48 
Slight 
trace 

0-42 
49-76 

7-00 


Total potash, KjO 
Iodine, lbs. per ton 
Carbon in insoluble part 


99-68 
23-17 
15i 
Nil 


100-02 
18-77 


99-85 
18-32 

28 

9-00 


introduced by Stanford in 1863, when works 
were erected in the outer Hebrides for the car- 
bonisation of the stems of tangle (L. digitala) in 
closed retorts, thus converting the tangle into 
charcoal and collecting the products of destruc- 
tive distillation, consisting principally of tar 
and ammoniacal liquor, in suitable condensers. 
A very porous charcoal is thus produced which 
contains all the iodine present in the seaweed 
employed ; when lixiviated it gives very white 
salts containing no sulphides. - The residual 
charcoal, after Uxiviation, does not resemble 
that from wood, which is principally carbon with 
a small percentage of ash, but in its composition 
and general character approaches animal char- 
coal obtained from bone. The following table 
shows the comparison : — 


— 


Seaweed 


Bone 


Carbon 

Calcium phosphate 
„ carbonate 
„ sulphate , 

Magnesium carbonate 

Alkaline salts 

Silica, &c. . 






52-64 
10-92 
15-66 

11^34 
5-70 
3-94 


11-77 

77-70 

1-43 

0-36 

1-09 
0-66 


\ 


lOOOO 


100-00 


The presence of m 
a peculiar characteristic 
seaweeds are rich in ma 
charcoal, as might be 
position, is an ezcelle 
odoriser. As compared 
is much lighter and mc 
has not replaced it aa 
from its high percentag 
stand the constant re-b 
works, and be improvec 

This process by car 
the islands of Tyree an 
for a number of years, 
crofters and cottars o 
quired, however, the e 
bonising works in each i 
tangle only was used, it 
sufficient supplies exc< 
Moreover, it was found 
some to completely ezl 


agnes 
! of tl 
^esiu 
expeo 
at de 

with 
re bu 

a de 
3of ca 
arnini 
Ibyt 
)onisa 
dNor 
ivith g 
f the 
rectio 
sland, 

was 
spt fl 
in pre 
iract 


iu 
lii 
m 
te 

00 

a 
Ik 

CO 

irl 

y 

ti 
th 

se 

n 
a 
d. 

01 

kCl 

th 


m carboi 
) charcoal 

salts. S 
d from it 
lorisei a 
[limal cha 
y, and tb 
loriser, a. 
)on it wot 
•equired h 
B treatme 
on was in 

and Sou 
lat benefit 

islands, 
of separs 
nd, as the 
lfficult to 
n a larg 
<ioe very 
e soluble 


late is 
, as all 
eaweed 
s com- 
ad de- 
rcoal it 
erefore 
though 
lid well 
a sugar 
nt. 

use in 
th Uist 
. to the 
It re- 
ite car- 
winter 
secure 
e area. 
rouble- 
iodides 



IODINE. 



145 



from the charcoal, and ultimately the process 
was abandoned in favour of the older and simpler 
method of_ kelp burning. A wet process of 
extracting iodine from seaweeds has also beein 
tried. It had been noticed by Stanford that the 
whole of the alkaline salts present in the sea- 
weed, and a considerable quantity of extractive 
matter containing dextrin and mannite, could 
be extracted from the fronds of the Laminaria 
or red seaweeds by simple maceration in cold 
water. The residue, which is the plant appar- 
ently unaltered, consists of a nitrogenous sub- 
stance resembling albumen, to which the name 
of ' algin ' has been given, and the algic cellulose 
or algulose, which represents the cellular fabric 
of the plant. The algin or alginic acid is 
iraioved by digesting it with solution of so- 
dium carbonate, which dissolves it as sodium 
alginate, leaving the algulose. The solution can 
be effected in the cold, but it is necessary to 
employ heat, otherwise it is impossible to filter 
off the algulose. A Taylor filter is the only one 
that can be employed, the filtration being ex- 
tremely difBcult on account of the great viscosity 
of the algin or sodium alginate and the extreme 
fineness of the cellular algulose. The process 
adopted is to boil the seaweed with sodium car- 
bonate, and filter ; the algulose is separated by 
filtration, and the filtrate is mixed with hy- 
drochloric acid, and the alginic acid is then easily 
filtered off; the solution is neutralised with 
caustic soda, evaporated to dryness, and car- 
bonised, the residue forming the 'kelp sub- 
stitute.' The alginio acid, which has a slight 



amber colour, is washed, bleached, and re- 
dissolved in sodium carbonate ; the resulting 
liquor, evaporated in a vacuum pan, forms the 
commercial alginate of soda or ' soluble algin.' 
By evaporation on glass plates or porcelain slabs, 
the algin is obtained in the form of a trans- 
parent flexible sheet, which, however, tends to 
crack as it approaches dryness, and by im- 
mersing this in a very dilute solution of hydro- 
chloric acid it is converted into alginio acid or 
' insoluble algin,' which, without altering its 
appearance, renders the sheet perfectly insoluble 
in water. The soluble algin is a definite salt of 
sodium, having the composition, when pure, 
CjjHjBOsaNjNaj. 

Commercial algin or sodium alginate re- 
sembles gum arable, and in the sheet form 
can scarcely be distinguished from gelatin 
from which it differs by the solution not gela- 
tinising, and by giving no reaction with tannin. 
It is distinguished from albumen by not coagu- 
lating on heating ; from starch by giving no 
colour with iodine ; from dextrin and gum 
arable by its insolubility in dilute acids. All 
mineral acids, and citric, tartaric, lactic, oxalic, 
and picric amongst the organic acids, precipitate 
alginio acid in a gelatinous form. 

It precipitates all the alkaline earths as 
alginates, with the exception of magnesium, the 
alginate of which is soluble. It precipitates 
nearly all the heavy metals as alginates, but gives 
no precipitate with mercuric chloride, nor with 
potassium silicate. The following analyses show 
the usual composition of the commercial algin : — 



— 


No. 1 


No. 2 


Average 


Water .... 
Organic matter . 
Sodium carbonate 
Neutral salts 
Insoluble ash 

Soda, Na^O i . . . 


17-13 

59-97 

18-32 per cent. 
2-98 ash 
1-60 22-90 


19-30 

68-13 

17-78 

2-77 

2-02 


per cent. 

ash 

22-57 


18-22 

59-06 

18-05 1 per cent. 
2-87 ash 
1-81 ) 22-73 


100-00 
10-71 


100-00 
10-40 


100-00 
10-55 



This substance, known as soluble algin, is sodium 
alginate, but potassium, ammonium, lithium, or 
magnesium alginate are all soluble algins, and 
scarcely distinguishable in appearance. These 
all present the form of thin flexible sheets, re- 
sembling gelatin, and having the same colour, 
but none are gelatinous. The solution of algin 
resembles that of gum arable, which in many of 
its applications it may be expected to replace ; 
it is quite soluble in cold water, but the solution 
takes about 12 hours to complete. It is so 
extremdy viscous that a 2 p.c. solution is as 
thick as a 50 p.c. solution of gum arable, and a 
5 p.c. solution is poured with difficulty out of a 
wide-mouthed bottle. Nearly aU the mineral 
acids precipitate alginic acid (CijHgjOsaNE) from 
the solution as a very gelatinous precipitate ; 
a 2 p.c. solution becomes semi-solid when thus 
treated. In this respect, it resembles a strong 
solution of egg albumen, and it can be employed 
for thickening colours in printing, or as a mor- 
dant in the same manner. Alginic acid is in- 
soluble in water, so that in dressing fabrics the 
soluble algin forms a flexible varnish, which can 
be converted into a lustrous hard glaze by 
Vol. III.— T. 



passing it through a weak mineral acid. This 
process, which would destroy the ordinary starch 
and gum dressings, renders it also permanent 
and insoluble in water, the fabric becoming 
waterproof. As the alginates of calcium, alu- 
minium, iron, &c., are all insoluble, the same 
effect is obtained by the use of solutions of these 
metals for the final wash. Alginio acid when 
dry resembles albumen, but it can be obtained 
also in thin transparent sheets, and readily 
coloured like gelatin, from which, however, it 
differs in being insoluble in hot water. It can 
also be obtained in blocks. Calcium alginate 
(OjeHjiCasNaOjs) resembles it, but is whiter, 
like bone. 

Aluminium alginate is very soluble in am- 
monia, and the aluminium ammonio-alginate is 
insoluble" when dry, so that it makes a cheap 
waterproof varnish. It forms a good mordant 
or dung substitute in dyeing. Copper alginate 
is soluble in ammonia, forming a beautiful blue 
copper ammonio-alginate, which is also insoluble 
when dry, and makes a varnish useful for water- 
proofing fabrics which are liable to decomposi- 
tion or to attacks of insects. 

L 



146 



IODINE. 



Peiric alginate is also soluble in ammonia, 
forming a bright red ferro-ammonio-alginate; 
insoluble when dry, and proposed as a styptic, 
and for administering iron internally. These 
metals are most completely precipitated from 
solution by sodium alginate. 

Nickel, cobalt, zinc, cadmium, manganese, 
chromium, uranium, silver, platinum, tin, arsenic, 
and antimony aliform soluble ammonio-alginates 
some of which are beautiful salts. Sodium 
alginate, mixed with a dichromate, is sensitive 
to light in the same way as gelatin, the mixture 
becoming insoluble in water after exposure to 
light. 

Alginio acid is a moderately strong acid, 
liberating carbon dioxide in the cold from the 
alkaline carbonates and from magnesiuny car- 
bonate ; in the latter case, the two insoluble 
substances in the presence of water form soluble 
magnesium alginate. The use of algin requires 
a, thorough Imowledge of its properties, on 
account of the numerous metallic salts which 
precipitate it, and with which it is therefore 
incompatible ; these reactions limit to a great 
extent the application of the substance in solu- 
tion as a substitute for gum and other bodies 
used for thickening purposes. 

Algulose or algic cellvdose contains no 
fibre, but consists of fine cellular tissue, which 
makes a transparent and very tough paper. It 
dries to a hard mass resembling ebony, but 
denser. 

The kelp substitute in this wet process was 
obtained by evaporating and carbonising the 
acid liquor from which the alginio acid has been 
precipitated, after neutralising it with caustic 
soda. It should contain all the iodine and 
potash salts of the weed but no sulphides, and 
should yield about 30 lbs. of iodine to the ton. 
At the same time, in spite of the advantages 
which apparently would attend the adoption of 
this process, the manufacturing costs are so 
high and the demand for the products, other 
than iodine and potash salts, is so limited, that 
the process has not met with success on the 
commercial scale. 

Lixiviation 0/ help. — Little improvement has 
taken place in this process ; the same simple 
method which has been in use for many years is 
still adopted in the Scotch works. 

The kelp reaches the factory in large masses ; 
these are first broken up into pieces about the 
size of road metal. The lixiviation is effected in 
rectangular iron vats with false bottoms ; the 
vats are coupled together and heated by steam, 
and treated exhaustively. The whole arrange- 
ment is similar in every respect to that adopted 
in the lixiviation of black ash in the Leblanc 
process of soda manufacture. The solution is 
run off at about 40° to 45°Tw. This is evapor- 
ated in open hemispherical oast-iron boiling pans, 
about 9 feet in diameter, and the salts which 
deposit are fished out. In some works this 
boiling down is effected in cylindrical wiought- 
iron closed pans, heated by a coil of steam pipes 
round the inside of the pan, and provided with 
mechanical stirrers to keep the deposited salts 
in suspension. When the liquor is concentrated 
to 62°Tw., the whole is run out into a settler to 
allow the salts to deposit, and the supernatant 
liquor is run off hot into the crystaUisers. In 



both cases the salt fished out or deposited is a 
crude potassium sulphate, which adheres a good 
deal to the pan and contains 50 to 60 p.o. of 
potassium sulphate, mixed with sodium sul- 
phate and chloride. The liquid is run into 
cylindrical iron coolers, and a crop of potassium 
chloride orystaUises out in two or three days. 
The mother liquor is again boiled down, and the 
salt deposited is fished out ; this salt is known 
as ' kelp salt,' and consists of sodium chloride, 
containing sodium carbonate equal to 8 to 
10 p.c. of alkali (NajO). The hot liquor is again 
run into the cooler, and another crop of potas- 
sium chloride is obtained. This process is re- 
peated several times, kelp salt being fished out 
in the boiling pan, and potassium chloride 
crystallised out in the cooler. These successive 
crops of ' muriate,'- as it is technically called, 
range in strength from 80 to 95 p.c. of potassium 
chloride. 

The mother liquor is now rich in iodine, and 
is treated for its extraction. The several salts 
all contain iodine, and require careful washing to 
obtain it. These salts are known as ' Kelp salt,' 
which was formerly used for reducing the strength 
of soda ash, but is now unsaleable, ' Sulphate,' 
which is sold at a low price for mammal pur- 
poses, and ' Muriate,' which is largely used for 
the manufacture of saltpetre, potassium carbo- 
nate, chlorate, and dichromate, and the prus- 
siates. The residual kelp waste formerly rcEilised 
about 5a. per ton, and was employed in the 
common bottle glass manufacture ; it consists 
principally of the carbonates of lime and mag- 
nesia, and some phosphates. It is all used as a 
manure in France, but in this country the 
farmers have always rejected it. 

The following is the analysis of an average 
sample : 

Salts of sodium and potassium . 1-50 

Carbon 3-09 

Calcium sulphate . . .3-06 

„ sulphide . . . 1-70 

„ carbonate . . . 20 '50 

♦Calcium and magnesium phosphates 6 -72 

Magnesium carbonate . . 6'89 

Magnesia 2-22 

Silicic acid and sand . . . 20-82 
Water 33-60 



Total .... 10000 

♦Containing phosphoric acid . .2-70 

The mother liquor, containing the iodides 
and bromides, also contains considerable quan- 
tities of sulphides, sulphites, and thiosulphates 
of sodium and potassium ; it is mixed with about 
one-seventh of its volume of sulphxirio acid, free 
from arsenic, about 145°Tw. (sp.gr. 1-726), and 
allowed to settle for 24 hours. This is effected 
in a closed lead-lined wooden vessel, provided 
with means to collect any sulphuretted hydrogen 
which may be given off. The sulphur compounds 
are decomposed, and a considerable deposit of 
sulphur takes place. This is known as ' Sulphur 
waste ' ; when dry it contains about 70 p.c. of 
sulphur, and is used in vitriol making. It also 
obstinately retains iodine, and long steaming is 
required to extract it. The liquor is strained off 
from the sulphur and run into the iodine still. 
This was formerly made of lead, but it now 
assumes the form of a deep hemispherical iron 



IODINE. 



147 



pot, heated by an open fire, and coveied with a 
strong leaden lid, to which are luted two earthen- 
ware arms ; these are coimected with two series 
of stoneware udells, about ten in each set. 
These udells have stone stoppers beneath to 
allow any water containing chlorine, bromine, 
and iodine to drain ofi. The apparatus is shown 
in Fig. 1. Manganese dioxide is added at 
intervals to the contents of the still, and the 
iodine is carried over with the steam. The 
reaction is as follows : 

2NaI+3HjSOi+MnOj 

= l2+2NaHSOi+MnS04+2H,0. 

Repeated distillations go on, without changing 



the udells, until these ate full of iodine, the bulk 
of which, and the best, is found in -the udells 
forming the centre of the series. The deposition 
of the iodine in successive layers squeezes much 
of the moisture out, and it is obtained in a firm, 
well crystallised form. The iodine on removal 
from the udells stiU contains moisture, and 
requires further treatment before the state of 
purity now demanded by consumers is attained. 
This old-fashioned process is the only one adopted 
in this countnr ; many others have been pro- 
posed and tried, but have not been commercially 
successful. Commercial iodine is always sent 
out in 1 owt. kegs ; the consumption is usually 
reckoned in kegs, which means 1 owl. It 




r'/ «■» — — 

^^ J ■< tt T' V m. 1 



: ti!!ff 




FlQ. 1. 



improves by keeping, becoming perfectly dry ; 
and as it can be stored in a small compass, and 
often represents considerable value, it has been 
a favourite commodity, for small speculative 
buyers. Bromine does not pay for the collec- 
tion, but if it were required the arms would be 
changed and a simple worm-condensing arrange- 
ment of lead or earthenware, or a series of stone- 
ware Woulff bottles attached : a further 
quantity of manganese dioxide would be added 
to the stiU, and the bromine distilled over. The 
liquor remaining in the stiU, and known as 
' waste still liquor,' is a dense acid liquid of 
sp.gr. 1-235 to 1-500, containing sulphates of 
iron, manganese, potassium, and sodium ; it is 
very troublesome to deal with and is run away 



The following is the analysis of an ordinary 
average sample. One gallon contained 3-327 lbs. 
of dry salts : — 





Liquor 


Dry salts 




per cent. 


per cent. 


Potassium sulphate 


5-13 


16-42 


Sodium sulphate 


910 


27-36 


Sodium chloride 


6-80 


20-43 


Manganous sulphate . 


3-75 


11-27 


Ferric sulphate . 


3 00 


9 02 


Calcium sulphate 


0-19 


0-57 


Magnesium sulphate . 


004 


0-12 


Sulphuric acid, free . 


5-26 


15-81 




33-27 


10000 



The iodine used for medicine is resublimed 
in small earthen or porcelain covered pans, and 
is then known as resublimed iodine ' ; it is 
obtained in large briUiant plates, and is an- 



hydrous. The pans employed must be shallow, 
as the vapour is very dense. 

When iodine is badly made it may contain 
white needles, which consist of iodine cyanide j it 
is now a rare impurity, but a very poisonous 
one. 

In France a difierent method is adopted. 
After the precipitation of the sulphur in the 
mother liquor by addition of hydrochloric 
acid in slight excess, and boiling for some 
time, the clear liquor is drawn off and diluted 
with water to 40''Tw. Chlorine is then passed 
into the solution, untU saturated, and the 
iodine is precipitated in a pulverulent form. 
Sometimes, instead of passing in chlorine, the 
calculated quantity of potassium chlorate is 
added to the solution ; by interaction with the 
hydrochloric acid this salt yields the chlorine 
necessary for the liberation of the iodine. Great 
care must be taken that too much chlorine is not 
added, as iodine chloride may be formed, and 
go off as vapour. The clear liquor is then drawn 
off, and the iodine repeatedly washed by decan- 
tation to remove the salts. It is drained in 
earthen vessels with perforated bottoms, and 
finally dried on porous tiles. It is then resub- 
limed. This is effected in ordinary earthenware 
retorts with short necks, and heated in a sand- 
bath in which they are completely immersed, 
the iodine being sublimed into earthen receivers. 
To recover the bromine from the liquor after 
extraction of the iodine, it is evaporated to dry- 
ness, and the residue is distiUed in a leaden 
retort with sulphuric acid and manganese di- 
oxide ; it is coUeoted in a receiver under strong 
sulphuric acid. The production of iodine in 
France has fallen ofi considerably; it is all 
used locally, either resublimed or made into 
potassium or other iodide, for which pur- 
pose the precipitated damp iodine suffices. 



148 



IODINE. 



In Norway there are now nine or ten, works 
engaged in the extraction of iodine from kelp. 
In Japan the chief kelp-prodacing districts aie 
the province of Shima and the island of Hokkaido, 
but nearly all fishery districts yield a little. The 
industry is more oi less scattered along the 
coast of Japan and is in the hands of many small 
piodncers, from whom the firms of iodine makers 
procure their supplies. 

Iodine from callehe. This mineral, the crude 
Godium nitrate of Peru and Chile^now forms by 
far the most important source of iodine. It con- 
tains iodine in 3ie form of sodium iodate, which 
accumulates in the mother liquors from which 
the sodium nitrate has been crystallised. The 
proportion of iodine in the caliche varies con- 
siderably in the different deposits; in some it is 
absent altogether, in others it runs as high as 
0-17 p.c. or 3-8 lbs. per ton ; usually it does not 
exceed 0-02 p.c. 

There are about 157 nitrate factories in Chile, 
but many of these are old and well worked out, 
and some are so badly situated as regards position 
and the raw material is of such a low grade, that 
they cannot work at a profit, and conseciuently 
are closed. At present about 101 factories are 
in operation, and their production of nitrate 
amounts to from 2,400,000 to 2,600,000 tons 
annually. Most of the factories are provided 
with plant for the extraction of iodine from the 
mother liquor, but, as theii powei of production 
of iodine is largely in excess of the world's power 
of consumption, the' manufacturers have com- 
bined to restrict the output. The basis of the 
power of production of these factories is put 
down at 115,000 Spanish quintals (about 6,100 
tons) per annum, whilst the total quantity con- 
sumed is only a fraction of this amount. A 
certain percentage of the iodine sold in Chile 
year by year is allotted to each factory, and 
consequently there are rarely more than a few 
months in each yeas during which iodine is 
made, and there is always a very large stock in 
hand. The exports are naturally kept as nearly 
as possible equal to the requirements, but if any 
large increase in consumption took place there is 
no doubt that Chile could supply foui or five 
times the quantity at present exported annually. 
The cost of recovering iodine as a by-product of 
the sodium nitrate industry is, in many cases, 
not more than from l^d. to 2d. per oz. 

It first came over in quantity in 1874, about 
497 kegs. In the following year, 900 kegs were 
exported, and since then the export has con- 
tinually increased. It was at first a very crude 
article, containing little over 60 p.c. of iodine, 
and a good deal was exported in the form of 
copper iodide. It is now, however, sent over in 
a pure state. 

The following is the analysis of one of the 
samples of iodine sent from Peru in 1874 : 

Iodine 



Sodium iodate 


. 1-26 


„ nitrate 


. 11-62 


Potassium nitrate . 


. 2-49 


„ stdphate 


. 1-78 


Iodine chloride 


. 3-34 


Magnesium chloride 


. 0-36 


Insoluble matter 


. 1-52 


Water . 


. 25-20 



100-10 



In 1877 the total production of iodine in 
Scotland was estimated at 1200 kegs; in France 
at 800 kegs. Thrpresent output does not reach 
these figures. 

Japan began to export iodine in 1902, when 
35 cwt. were sold. In 1904 the quantity ex- 
ported was 612 cwt., in 1906 (consequent upon 
a fall in the price of iodine) only 196 cwt., and 
in 1907, 306 cwt. 

In 1882, the export of iodine from Chile was 
4116 cwt., in 1901 it had risen to 5280 cwt., and 
last year it amounted to 7900 cwt., of a value of 
about 350,0002. This is about four times the 
present total production of the rest of the world. 
The quantity of iodine sold throughout the 
world in 1887 was 6375 cwt., of which about 
1000 cwt. were used in colons making. The 
present average annual consumption may be 
taken at nearly 10,000 cwt. 

The final mother liquor, or ' aqua vieja,' from 
which the sodium nitrate has been crystallised, 
contains sodium iodate, nitrate, chloride, and 
sulphate, and magnesium sulphate. A good 
liquor contains about 0-3 p.c. of iodine. 

It is run into wooden vats and the iodine is 
precipitated; the agent employed is sodium 
bisulphite in solution. The exact amount of 
iodine in the mother liquor is estimated, and a 
definite quantity of the solution is added to 
completely precipitate the iodine. As the 
bisulphite solution is run into the ' aqua vieja,' 
the liquid is stirred either by wooden paddle- 
wheels 01 by ail forced up from perforated pipes 
at the bottom of the tanks. The latter method 
is quicker and more efficient, but the air carries 
away some of the iodine from the solution. The 
solution is then neutralised by addition of * sal 
natron' liquor «nd agam well stirred. After 
some time, most of uie iodine settles to the 
bottom of the tank; any little that remains 
floating is removed by a calico bag at the, 
end of a stick. The supernatant Uquid is 
drawn ofi and used over again with the nitrate 
liquors. 

The iodine is washed with water, and pressed 
into thick cakes. It then contains 80 to 86 p.c. 
of iodine and 6 to 10 p.c. of mineral matter, and 
requires to be purified by resublimation. This 
is efiected in a ca^-iron retort, to which eight 
earthenware condensers or udells are attached in 
series. The retort is heated by a slow fire, and 
when the operation is completed the retort is 
allowed to cool, and the iodine removed from the 
udells. It is thus obtained pure. The complete 
plant is shown in the descriptive plans Figs. 2 
and 3. 

The sodium bisulphite is prepared by passing 
the fumes of burning native sulphur into a solu- 
tion of ' sal natron ' or sodium carbonate. The 
sulphur, which is one of the many minerals 
found in this interesting region, is burned on an 
iron plate in a plain iron oven, and the fumes 
drawn by a steam injector into perforated pipes 
in the solution of sal natron. The manufacture of 
this substance is also peculiar to the district. 
It is obtained by burning together 86 parts of 
crude sodium nitrate, obtaJned from the ' aqua 
vieja ' tanks, and 16 parts of coal. The mixture 
is made in the form of a cone 5 feet high, with a 
space of 2 feet dug out round the base. It is 
saturated with water and ignited ; the sodium 
carbonate thus formed fuses and runs out into 



IODINE. 



149 



the pit. _ It is dissolved in water, and the 
solution is pure enough for use in this process, 
the impurities consisting of sodium sulphate 



and chloride, the unburnt coal being left in 
the residue undissolved. 

Uses of iodine. — About one-fifth of the total 




consumption of iodine is employed in the manu- 
facture of aniline colours j a good deal of this is 
recovered and used again. It is principally used 
in the manufacture of Hofmann violet, and 



aniline green in the form of methyl iodide; 
also for making erythrosin and the blue shade 
eosins, in which iodine is made to react upon 
fluorescein. Some substitution products are 



150 



IODINE. 



occasionally made, such as the ethylated chrys- 
aniline. A small quantity is used in photo- 
graphy, but the bulk of the iodine of commerce 
is employed in medicine. Iodine, iodoform, 
and the iodides of arsenic, iron, lead, mercury 
(red iodide), potassium, sodium, and sulphur 
are all official in the British Pharmacopceia ; 
the preparations employed will be referred 
to under their respective names. Hydriodic 
acid, ethyl iodide, and iodides of ammonium, 
cadmium, mercury (green iodide), and starch 



are also used in medicine, and each will there- 
fore be noticed. Iodine, if pure, should sublime 
without residue, and the portion subliming ifirat 
should not include any slender colourless prisms 
emitting a pungent odour (cyanide). The 
British Pharmacopoeia directs that one gram 
dissolved in 50 o.c. of water, containing two 
grams of potassium iodide, should require for 
complete decolouration at least 78-4 c.c. of the 
volumetric solution of sodium thiosulphate, 
which contains 24-8 grams of the salt in 1000 c.c. 




_B 



SECTIONAL PLAN OF OVEN. 




SECTION THROUGH A.B. 









:V^v;.-..,"lr 




J l; > -^■■- -III 


ir 




" 


m^ 




II III 


V. 




; 



SECTION OF EARTHENWARE RECEIVER, 



B ETO RT. 



E J ECTOR, 

'/» Full Sixe . 



Fia. 3. 



It is employed in the Q. P. in the form of 
Tinctura iodi, 1 in 40, Liquor iodi, 1 in 24, 
Linimenium iodi, 1 in 8, Vnguerdum iodi, 1 in 31, 
and Vapor iodi. In the tincture and the liquor, 
it is dissolved with potassium iodide in rectified 
spirit and water respectively. The liniment con- 
tains the same ingredients dissolved in rectified 
spirit, with the addition of glycerol. In the 
ointment the same ingredients are employed, 
substituting lard for the spirit. The vapour is 
for the inhalation of iodine; the tincture with 
water is placed in a suitable inhaler and gently 
heated. 

A volumetric solution of iodine dissolved in 
potassium iodide is used in the laboratory for 
titrating solutions of arsenious acid, of sulphu- 
rous acid, and sodium thiosulphate. It contains 
12-7 grams of iodine in 1000 c.c, and corresponds 
to 1-7 gram of sulphuretted hydrogen, 3'2 grams 



of sulphur dioxide, and 4-95 grams of 
arsenious oxide. Iodine is also used for 
testing oils, which diSer as to the amount ab- 
sorbed, and some can be distinguished from 
others by this means {v. Oils, Fixed and Fats). 
Other unofficial preparations of iodine are 
also employed in medicine. Olycerinum iodi is 
iodine dissolved in glycerol, used for external 
application. Pigmentum iodi. Coster's paste, is 
iodine dissolved in light oil of wood tar, and 
used for ringworm. Tinctura iodi decolorata is 
a 'tincture made with rectified spirit, and in 
which the iodine is decolorised by ammonia. 
It is used for chilblains. CoUodium iodi is 
flexible collodion containing 30 grains of iodine 
to the ounce, and is very useful for painting on 
wounds. Carbolised iodine solution is a colour- 
less mixture of tincture of iodine, phenol, and 
glycerol in hot water ; it is used as a gargle or 



IODINE. 



151 



pigment in diphtheria, and internally for Asiatic 
cholera. 

MaLicindl properties of iodine. — ^Iodine was 
first employed in medicine in the form of burnt 
sponge, a remedy long used in treating goitre. 
When administered internally it is usually in 
combination with an alkali ; taken alone it is an 
irritant poison. It is a most powerful alterative, 
impoverishing the blood and stimulating the 
absorbents. It is antisjrphilitio and antiscro- 
fulic. In syphjlis, scrofula, and chronic rheu- 
matism it is largely used, and especially in 
swellings of the joints and enlarged glands, 
which are also treated by painting externally 
with tincture of iodine, in which it acts as a 
counter-irritant. It has a remarkable power in 
expelling both mercury and lead from the system. 
The vapour mixed with steam from hot water is 
useful in inhalation for many affections of the 
air passages. Long-continued use may give rise 
to the depressing nervous train of symptoms 
known as iodism, and for which belladonna is 
employed as an antidote. Copious drinks of 
solution of starch form the antidote in oases of 
poisoning. Used alone, iodine is a powerful dis- 
infectant and decoloriser, acting in the same 
way as chlorine. It may be allowed to evaporate 
spontaneously, but is very apt to colour the 
sheets, blinds, or anything dressed with starch ; 
it is also used in candles, the burning of which 
volatilises it. 

Hydrogen iodide HI is a colourless gas, 
very soluble in water and resembling hydro- 
gen chloride ; it forms dense white fumes 
in the air; its sp.gr. is 4-3737. It liquefies 
under pressure, and solidifies at —65°. It is 
composed of equal volumes of iodine and hydro- 
gen, and contains 99-2 p.o. of its weight of iodine. 
The aqueous solution is colourless, but on expo- 
sure to air it becomes coloured by the deposition 
of iodine from oxidation. It is decomposed by 
sulphuric and nitric acids, and by chlorine and 
bromine, which set the iodine free. 

The following table shows the relative per- 
centage of iydriodic acid at different specific 
gravities : — 



Sp.gr. at 15° 
1-708 
1-551 
1-442 
1-297 
1-175 
1-083 



Per cent, of acid 
61-9 
47-2 
39-2 
30-3 
18-5 
6-9 



It is usually prepared in solution by passing 
sulphuretted hydrogen into water in the presence 
of iodine : HjS+I=2HI+S. At first the action 
is slow on account of the deposition of sulphur 
covering Up the iodine and preventing its solu- 
tion ; the hydriodie acid when formed, however, 
dissolves an increasing proportion of iodine, and 
by the gradual addition of iodine and water as 
the action progresses, large quantities of hy- 
driodie acid may thus be obtained up to a sp.gr. 
of 1-66. 

A modification of this process for very pure 
acid has been proposed by Winkler. The iodine 
is dissolved in carbon disidphide, and the solution 
covered with a stratum of water ; when the sul- 
phuretted hydrogen passed into the mixture, the 
hydriodie acid (Sssolves in the water, and the 
sulphur in the carbon disulphide. The aqueous 



solution only requires boiling for a few minutes 
to expel the sulphuretted hydrogen, and to 
obtain the hydriodie acid quite pure. Hydriodie 
acid is employed in the manufacture of some of 
the iodides, and is used in medicine in the form 
of syrup. 

Another method was suggested by Kolbe. 
One part of amorphous phosphorus is added td 
16 parts of water in a tubulated retort filled with 
carbon dioxide, and 20 parts of iodine gradually 
added. The resulting liquid is allowed to stand 
and then heated for a short time, cooled, mixed 
with 4 parts of water and distilled. It yields a 
colourless acid free from uucombined iodine : 
P4-6H-4HaO=5HI+H,P04. 

Iodic acid HIOj. This acid is usually pre- 
pared by boiling iodine in strong nitric acid, 
free from nitrous acid. Iodic acid is deposited 
in crystals. When heated it gives off water, 
and iodine pentoxide IjOj is obtained in small 
white crystals. It is very soluble in water, and 
easily decomposed by reducing agents forming 
hydriodie acid and free iodine. 

The iodates have the general formula 
MIO3. 

Potassium iodate KIO3 forms small white 
cubic crystals. Sodium iodate NalO, crystal- 
lises in small eight-sided prisms. Both salts 
are poisonous. Both are obtained in consider- 
able quantity in the manufacture of the re- 
spective iodides by No. 2 process as described 
below. The iodates can easily be separated 
by taking out the first salts deposited on evapo- 
ration, as these are less soluble than the iodides. 
If iodic acid were required on the large scale, it 
could be easily made as a by-product of the 
iodide manufacture by crystallising out the 
iodate before fusion, and precipitating it with 
barium chloride as barium iodate. TMs is then 
decomposed by sulphuric acid. It has, how- 
ever, no commercial application. 

Iodine trlehloride ICl, is obtained in orange- 
yeUow crystals by passing chlorine into a flask 
containing iodine vapour sublimed from a small 
retort. It is a very active disinfectant and ger- 
micide in solution of 1 to 1000. It has been 
used in medicine internally. In contact with 
organic matter, chlorine and iodine are liberated 
in a nascent state. 

Iodine cyanide, or Iodide of cyanogen, CNI. 
This very poisonous substance is interesting 
as forming an occasional impurity in com- 
meicial io(£ne ; it is very seldom met with now, 
and ought never to be present if the manufac- 
ture is properly carried out. Its occurrence is 
probably due to an insufficient addition of oil 
of vitriol to the saturating vat or to the iodine 
stUl. It is usually prepared in the laboratory 
by the distillation of iodine with mercuric 
cyanide. When present in iodine it presents 
the appearance of exceedingly fine silky needles, 
colourless, and very volatile, even at ordinary 
temperatures, and with a penetrating pungent 
odour which excites tears. It sublimes with- 
out change. It is sparingly soluble in water, 
easily so in alcohol, and in ether, and also in fixed 
and volatile oils. The aqueous solution does 
not give the starch reaction of iodine, nor does it 
precipitate silver nitrate. 

Sulphur iodide SJa is a dark crystalline sub- 
stance, obtained by gently heating in a glasf flask 
1 part of sulphur with 4 parts of iodine until the 



162 



JODINE. 



mixture liquefies ; the flask is then broken, and 
the crystalline mass remOTed. It is insoluble in 
water, but soluble in glycerol. It has the 
odour and staining properties of Iodine. It is 
used in medicine externally in skin diseases 
applied in an ointment. The official prepara- 
tion is Unguentum svlphuris Midi, containing 
30 grains to 1 ounce. 

Arsenious iodide, or Iodide of arsenic, Asl,. 
This salt forms small orange-coloured crystals, 
soluble in water and in alcohol ; it has a neutral 
reaction, and gives a yellow precipitate with 
sulphuretted hydrogen. Heated in a test-tube 
it almost entirely volatilises, violet vapours of 
iodine being set free. 

It is prepared by direct combination of me- 
taUio arsenic and iodine, or by evaporating 
together to dryness solutions of arsenious and 
hydriodio acids. The dose is j, of a grain ; 
and the Pharmacopoeia preparation is Liquor 
arsenii et hydrargyri iodldi, about 1 grain in 
100. 

Nitrogen iodide NjHal, or NHj-NI, is a 
dark brown powder, obtained by adding iodine 
to excess of solution of ammonia. It is a most 
violent explosive, but its action is uncontrollable, 
and it is impossible to keep it in safety. It has 
therefore found no commercial application, but 
has been proposed as a chemical photometer 
on account of the ease with whicli it is de- 
composed by light in presence of excess of 
ammonia (v. Guyard, Ann. Chim. Fhys. [vL] 
1, 368). 

Ammonium iodide NHJ. This is a white 
crystalline salt, very deliquescent and becoming 
yeUow on exposure to air. It is prepared by 
saturating hydriodic acid with ammonia, oi by 
decomposing iodide of iron with ammonium 
carbonate and filtering ofE the iron precipitate. 
The solution in either case is evaporated and 
set aside to crystallise. It is used in photo- 
graphy, and also in medicine instead of potas- 
sium iodide, especially in rheumatism, as causing 
less depression than the potassium salt. It 
must be kept from the access of light and air, as 
iodine is freely given off. It is soluble in 
alcohol. 

Potassium iodide, or * Hydriodate of potash,' 
KI. This is the most important of the iodides, 
and forms a considerable article of manufacture, 
as the greater portion of the iodine of commerce 
goes into consumption in this form. It is a 
white, colourless, and odourless salt crystallising 
in large cubes, and permanent in the air. It 
contains no water of crystallisation, and is very 
soluble in water, dissolving in two-thirds of its 
weight. It is also soluble in alcohol. There 
are three methods employed in the manu- 
facture. 

1st. Hydriodic acid is saturated with potas- 
sium carbonate, and the solution evaporated 
and crystallised. This is the most direct method, 
and there is no loss ; it gives a pure product, 
but ft is expensive and tedious. 

2nd. Iodine is dissolved in solution of caustic 
potash. This produces a mixture of potassium 
iodide and potassium iodate ; the reaction is 
3l2-f6KOH=5KI-fKIO,+3H20. Thesolution 
is evaporated to dryness, a little charcoal is 
added, and the product fused in an iron pot at a 
red heat untQ all the iodate is decomposed, and 
potassium iodide alone remains, - The mass 



is dissolved in water, the solution filtered and 
crystallised. 

3rd. Iodide of iron is first prepared by the 
addition of iron borings and iodine to water ; 
the latter must be added gradually to keep down- 
the temperature ; the solution is filtered, mixed 
with potassium carbonate and the iron precipi- 
tate washed and filter-pressed. The solution is 
then evaporated to dryness and the residue re- 
dissolved and crystallised. 

This process is that most commonly adopt-ed 
by manufacturers. The crystallisation is per- 
formed in enamelled iron pans, surrounded by 
a steam jacket in brickwork, and very gradually 
cooled. The best crystals are obtained on fiuted 
glass rods suspended in the liquid. 

The second process is that directed by the 
British Pharmacopoeia. 

Potassium iodide or ' Hydriodate,'' as it is 
often called, is used in photography, but medicine 
is the principal outlet, and requires a large 
consumption. It is a powerful alterative, 
diuretic, and absorbent ; and is much adminis- 
tered internally, especially in rheumatism and 
syphilis ; the dose is 6 to 10 grains, but doses 
of 100 grains have been given in some cases. 
Its properties are similar to those of iodine. 
As iodine is freely soluble in potassium iodide 
solution, it presents an excellent form foi its 
internal administration. 

It must contain no iodate; this is easily 
detected by the addition of tartaric acid and 
starch solution, which sets free hydriodic acid, 
and if there be any trace of iodate present, free 
iodine is liberated, as shown by the blue colour 
of the iodide of starch. Potassium iodide should 
not contain water, and therefore should not lose 
weight when heated ; it should contain no sul- 
phate, and therefore give no precipitate with 
barium chloride insoluble in nitric acid. A 
feeble alkaline reaction from the presence of a 
slight trace of carbonate, indicated by cloudiness 
with lime or baryta water, soluble in nitric acid, 
is allowed by the London Pharmacopoeia (but 
not by the German) as tending to retain the 
colour of the iodide when long kept. Chlorides 
of potassium or sodium are a common impurity ; 
the presence of a chloride is shown by precipita- 
ting with silver nitrate, and agitating the pre- 
cipitate with ammonia. The ammonia solution 
should give no precipitate with nitric acid. One 
gram requires for complete precipitation 60-2 
c.c. of a volumetric solution of silver nitrate con- 
taining 17 grams of the salt in 1000 c.c. It is 
almost impossible to obtain this salt, when made 
on the large scale, quite free from chloride (the 
B. P. allows a ' very little ') as potassium car- 
bonate cannot be prepared in quantity without 
it ; a good iodide contains : 



Potassium iodide 


a 


. 99-4 


„ chloride . 


, 


. 0-2 


Water . 


, 


. 0-4 



100 

This salt is oflScinal in the following pre- 
parations ; the number of grains in one fluid 
ounce is given in each case. Idnimentum iodi 
22 grains; Linimenium potassii Midi cum 
Sapone 64| grains; Liquor iodi 33 grains; 
Tinctura Mii 11 grains; Unguentum iodi 16 
grains; Unguentum potassii iodi 54 grains. 



IODINE. 



ISS 



Potassium iodide is sometimes administeied in 
large doses, and it is important medicinally that 
it should contain noiodate.asthis salt is poison- 
ous : it must not be presoribed in mixtures con- 
taining potassium chlorate, for this Salt decom- 
poses it, forming iodate. 

Sodium Iodide Nal. This salt is obtained as 
a deliquescent white crystalline powder, soluble 
in two-thirds of its weight of water. It may be 
prepared by the same methods as the correspond- 
ing potassium salt ; ' that from ferrous iodide is 
usually employed, and the solution is simply 
evaporated to dryness. It crystallises in an- 
hydrous cubes and also in hexagonal plates, 
having the formula HaI,2H20. It is used in 
medicine foe the same purposes as potassium 
iodide, but the principal application is as 
a precipitant of silver and gold from the 
weak copper ores of the Tharsis and other 
copper-extracting companies. The same tests 
as with the potassium salt may be used 
for its purity ; I gram requires 66 c.c. of the 
volumetric solution of silver nitrate foe com- 
plete precipitation. 

Ferrous iodide, or Iodide of iron, Fel^. 
This is a crystalline green ddiquescent mass. 
It is only employed in medicine, and more 
particularly in the form of syrup of iodide 
of iron, in which it can be better preserved. 
The official preparations are Pilula ferri iodidi, 
and Syrwpus ferri iodidi, containing Si-i grains 
of the ssdt in one fluid ounce. It is a tonic 
alterative useful in aneemia of scrofulous patients, 
especially children. 

A similar syrup of manganese iodide is also 
sometimes used in medicine. 

Zinc iodide Znlj. An easily fusible com- 
pound which subhmes in needles. It is prepared 
in the same way as the iron salt, and obtained by 
evaporation as a white crystalline deliquescent 
salt. It is sometimes used in photography. 

Lead iodide, or Plumbic iodide, Pblj. This 
is a brilliant yellow powder, made by precipi- 
tating a solution of lead nitrate with potassium 
iodide, and washing and drying the precipitate. 
By boiling the powder in water, and allowing 
the solution to cool, it is obtained in bright 
yellow crystalline sctdes. It is employed in 
medicine externally in the form of ointment and 
plaster. The official preparations are Em- 
plastrum plwnibi iodidi, 1 part in 9 ; and Un- 
guentum plumbi iodidi, 1 part in 8. 

MercuTOUs iodide Egl, oi Cfreen. iodide of 
mercury, is a green insoluble powder, which 
darkens on exposure to light. It is prepared by 
rubbing together in a porcelain mortar the 
equivalent proportions of mercury and iodine, 
and moistening the mixture with alcohol until 
the metallic globules cease to appear and a 
green powder is obtained. This must be dried 
in the air in a dark room, and preserved in a 
bottle put away from the light. It can be ob- 
tained in yellow crystals by sublimation. It is 
insoluble in water and alcohol. It is employed 
in medicine in doses of 1 to 3 grains. It is an 
irritant poison and is used in syphilis. 

Mereuric iodide, or Sed iodide of mercury, 
Hgl^. This is a bnUiant scarlet powder, known 
as Chinese vermilion. It may be prepared in 
the same manner as the green iodide, using 
double the eqmvalent of iodine ; but a better 
product is obtained by precipitation. A solution 



of mercuric chloride, or corrosive sublimate, is 
precipitated with potassium iodide, both salts 
being dissolved in boiling water ; the precipitate 
is washed and dried over the water-bath. By 
sublimation it may be obtained in large and 
beautiful crystals, which when hot are yellow, 
but reassume their scarlet colour on cooling. 
It is insoluble in water, but very soluble in 
solution of potassium iodide. This solution con- 
tains a double iodide of mercury and potassiuin 
and is used in analysis as a precipitant for alka- 
loids. It forms a pigment more brilUaut than 
vermilion, but it is not much used for tiiis pur- 
pose, as it is easily altered by exposure. It is 
employed in medicine, especially in syphilis, in 
doses of a thirty-second to an eighth of a grain, 
and also externally as an ointment. The official 
preparations are Liquor arsenii et hydrargyri 
iodidi, containing 1 grain in 100 grain measures, 
and VnguerUum hydrargyri iodidi ruhri, con- 
taining 1 part in 28. It has been recently 
introduced as a germicide for washing wounds, 
instead of corrosive sublimate, which is not 
so effective and is more poisonous. It has 
also been used as an antuecmentive in tan- 
ning. 

Bismuth iodide BI, is a red powder obtained 
by precipitation from bismuth nitrate by 
potassium iodide. It has been introduced 
into medicine as a substitute for iodoform in 
treating wounds. It has no odour. Tliis iodide 
is soluble in potassium iodide, forming a double 
iodide employed in analysis as a precipitant for 
alkaloids. 

Silver iodide Agl. This salt occurs native, 
in hexagonal crystals, as iodargyrite or iodyriie. 
It is obtained by precipitation from a solution 
of silver nitrate and any soluble iodide. This 
salt is not employed commercially in this form- 
It is the active salt of iodine which is used in 
photography, but it is" always produced on the 
plate or the paper. It is the form in which iodine 
is often precipitated and weighed. It is almost 
insoluble in ammonia, but soluble in potas- 
sium iodide and cyanide, and in sodium thio- 
sulphate. 

Palladium iodide Pdl^- This is a dark-brown 

Eowder, interesting as the most insoluble salt of 
ydriodic acid, and as a form in which it is 
estimated in analysis. 

Cuprous iodide, or Iodide of copper, Cn2l2. 
When solutions of potassium iodide and cupric 
sulphate are mixed, only half the iodine is' pre- 
cipitated as cuprous io(£de, the other half being 
set free, according, to the following equation : 
2CUSO4 -f 4KI = Cujia -f la + 2K2SO4. It is 
necessary, therefore, to add a reducing agent 
as sulphurous acid or sodium hyposulphite, 
but ferrous sulphate is usually employed ; the 
whole of the iodine is then thrown down as 
cuprous iodide 
2CuS04+2FeSOi-f2KI 

=Cu2la+KjSOi-l-Fe2(S04),. 
The former reaction was proposed by Soubeirau 
as a method of obtaining iodine from kelp liquors, 
but it has not been much used. 

Cuprous iodide is a white crystalline solid, 
insoluble in water ; on exposure to a red heat 
it fuses to a brown mass. The iodine can be 
separated from it by heating it with manganese 
dioxide or strong sulphuric acid. Or it may bo 
decomposed by boiling with water and zinc. 



154 



IODINE. 



which yielda zinc iodide and metallic copper. 
Ol it may be treated with potaGsium or sodium 
hydroxides or carbonates, which decompose it, 
forming cuprous oxide and potassium or sodium 
iodide. With ammonia it combines, forming- 
ammonio-cuprous iodide CuI,2NH8; a white 
crystalline powder. 

Iodide of starch, or Iodised starch, is a dark 
blue powder obtained by triturating iodine with a 
little water and adding gradually starch in 
powder until it assumes a deep and uniform 
colour, and drying at a low temperature. It is 
decolorised at 100°. It is used in medicine as 
a mild form of administering iodine internally, 
in doses of half a drachm to four drachms. In 
the form of a paste it is employed to cleanse and 
heal foul sores and ulcers. 

Estimation of iodine. — ^The violet vapour of 
free iodine is characteristic, and there are also 
four very sensitive tests for iodine and iodides : 
for the former the blue colour test with starch, 
and the crimson solution in chloroform, benzene, 
or carbon disulphide ; for the latter the precipita- 
tion as silver or pallaidum iodide. All these 
can be employed in estimating iodine, the colour 
tests by comparison with standard solutions, and 
the gravimetric tests by weighing the iodine as 
silver iodide or palladium iodide. Insoluble 
iodides must be converted into alkaline iodides 
before precipitation by silvei nitrate or palla- 
dium chloride. This may be efleoted by fusing 
with sodium carbonate, or preferably by a mix- 
ture of this and potassium carbonate. Another 
method for a metallic iodide is to suspend it 
in water and pass sulphuretted hydrogen through 
th% mixture ; the metal is precipitated as a sul- 
phide, and hydriodio acid formed. Silver iodide 
is generally heated with zinc and dilute sulphuric 
acid, the silver is reduced to the metallic state, 
and zinc iodide remains in solution. 

If the iodine exists in the form of a soluble 
iodate it must be reduced to an iodide by sul- 
phurous acid. With organic iodides it is usual 
to ignite with pure sodium hydroxide. 

In the colour tests, the iodine must be set 
free by bromine, chlorine, or, preferably, uitro- 
sulphurio acid. The starch method, owing to 
the easy decomposition of the iodide of starch, 
is not generally available, but the separation 
of the iodine from solution by a solvent forms 
a process of great accuracy, of easy and rapid 
execution, and of general application. In 
estimating the iodine in kelp oi seaweed ash, 
or kelp substitute, the following process is 
adopted. Kelp is not an easy cargo to sample. 
There is often great difference in the value of 
the large masses forming the cargo. ' Stones and 
sand are a frequent cause of annoyance ; stones 
are often found fused into the centre of a block 
of kelp, and forming most of the block. These 
can only be detected by breaking Up all the large 
pieces. With seaweed ash, or charcoal, or kelp 
substitute there is no difficulty. Where there is 
much sand the kelp is more friable. The sand 
is generaDy composed of shells, and is mostly 
carbonate of lime ; but jt is sometimes quartz, 
flint, or other form of silica. To insure an 
accurate sample, about 100 lbs. are carefully 
picked from a cargo of, say, 100 tons, and ground 
up. A portion of this is finely powdered and 
kept as a sample for reference. Of this, 6 grams 
are taken to estimate the moisture, another 



5 grams are taken to estimate the soluble 
matter, the carbon, and the ash, also the potash 
and the iodine in the soluble matter. The kelp 
is treated with about 75 c.c. of hot water, which 
dissolves little or none of the oxysulphides. 
This operation is repeated and the residue 
washed, and the solution made up to 260 c.c. 
In a portion of this the potash ia estimated by 
platinum tetrachloride. For estimating the 
iodine, one-tenth part or 26 c.c, equal to 0-5 
gram of kelp, is taken. This will not contain 
more than 6 milligrams of iodine, generally 
about 2 milligrams, often only 0-6 milligram. 
If the amount exceeds 6 milligrams, it is 
advisable to' dilute the solution with an equal 
bulk of water. Five c.c. of carbon disulphide 
are then added and a few drops (one to three) of 
nitro-sulphurio acid dropped in. This reagent is 
prepared by treating starch with nitric acid, and 
passing the nitrous fumes into sulphuric acid of 
1-843 sp.gr. to saturation. The mixture keeps 
perfectly well. The testings are performed in 
large even test tubes, and compared with 
graduated standard solutions of potassium iodide 
treated in precisely the same manner. By this 
method isulmth part of iodine is easily detected 
and measured, and up to T!!im!^li F^i^t the esti- 
mation is very accurate. It has several advan- 
tages over the use of starch, as besides the 
introduction of an organic substance liable to 
change, the blue colovir of the iodide of starch 
is distributed over the whole liquid, and when 
dilute can only be seen by looking down the 
length of the tube. Moreover, the solution is 
not transparent, and the indications are not 
sharp enough for accurate quantitative work, 
though useful often in testing. The carbon 
disulphide method is quite as sensitive, and the 
iodine is removed from the solution and concen- 
trated in a sixth of the volume at the bottom of 
the tube. The maximum effect, which takes 
time with the starch, is immediate in this case. 
The carbon disulphide solution of iodine can be 
removed, and the iodine recovered from it by 
an alkali for further experiment if desired, but 
it is quite unnecessary for accurate results. It 
is usual to remove it from the disulphide by zinc 
in the presence of water, so that the reagent can 
be used over and over again. Many years of 
experience of this and other processes have 
shown that this is the only one to be relied on 
where many such estimations have to be per- 
formed daily, especially in kelp and its products, 
which contain such a small proportion of iodine. 
If the iodine is to be determined in a seaweed or 
other organic material, the sample must always 
be carbonised in a small iron retort or close 
crucible, and not burnt to ash in an open 
crucible. The salts are washed out from the char- 
coal, and the carbon and ash estimated by burn- 
ing the residue. If this be not done, it is almost 
impossible to completely burn away the carbon 
in the presence of so much alkaline salts which 
at a high temperatur? fuse and cover it over. 
If, moreover, a long time is taken, as it must be, 
over an ordinary Bunsen burner, a large portion 
of the potash and all the iodine may be easily 
burnt off. If the salts contain magnesium, as 
all those from seaweeds do, it is necessary to 
make sure that there is an excess of alkali pre- 
sent, or the iodine will be rapidly burnt off. 
In kelp and seaweed there always is sufficient 



IODINE. 



166 



alkali, and this precaution is unnecessary, but 
where the object is to estimate iodine in organic 
substances containing it in minute traces, more 
caustic soda should always be added before car- 
bonising. As all seaweeds also contain soluble 
sulphates which become reduced to sulphides 
and oxysulphides when burnt to ash, carboni- 
sation presents another advantage, as it prevents 
this change. 

Palladium chloride is the only reagent which 
can be relied on for the direct gravimetric 
estimation of iodine in mixed liquors containing 
chlorides and bromides. The kelp liquor must 
be mixed with hydrochloric acid and set aside in 
a warm place till the sulphur compounds are de- 
composed, it is then filtered oS and precipitated 
with palladium chloride, and allowed to stand for 
some time. The black precipitate of palladium 
iodide may be wasled with hot water, and lastly 
with a little alcohol, dried at a gentle heat, and 
weighed on a tared filter ; 100 parts contain 
70-46 parts of iodine. Or it may be ignited in a 
platinum crucible, and the iodine calculated 
from the weight of the palladium left ; 100 parts 
of palladium are equal to 238-5 parts of iodine. 
If chlorine is also to be estimated in the same 
liquid, palladium nitrate must be substituted for 
the chloride. If bromine is also present the 
chloride must be used, or a soluble chloride must 
be added, or the bromine will be precipitated 
with the paUadium iodide. This method gives 
discordant results with kelp, on account of 
the cyanides often present. Free alkalis, chlor- 
ine, and bromine also prevent the precipitation. 

In ' caliche ' the iodine exists as an iodate, 
and this must be first reduced to an iodide 
by sulphurous acid or sodium bisulphite. 
There are several methods of estimating iodine, 
bromine, and chlorine, directly and indirectly, 
when present together. A very simple method 
of separating these elements directly is to distil 
over the iodine first by boiling with ferric sul- 
phate ; it may be condensed in solution of potas- 
sium iodide and titrated with sodium thiosul- 
phate. The bromine is then separated from the 
residue in the retort, which has been allowed to 
cool, by gently warming the solution after addi- 
tion of potassium permanganate, and distilling 
it into solution of ammonia in excess, in which 
it is titrated with an acid ; or estimated gravi- 
metrically by precipitation as silver bromide. 
The chlorine can be estimated in the residue or 
by difference from a determination of the total 
quantity of chlorine, bromine, and iodine in the 
original substance by precipitation as silver salts. 
Another method is to distU over the iodine with 
a concentrated solution of potassium dichrom- 
ate ; after the iodine is removed the addition of 
a little sulphuric acid to the retort will set free 
the bromine, the chlorine can then be determined 
as in the last process. 

Field's method of separating these three 
halogens is to divide a solution into three equal 
parts ; each portion is precipitated by silver 
nitrate. No. 1 is washed, dried, a^d weighed. 
No. 2 is digested with potassium bromide, then 
washed, dried, and weighed. No. 3ns digested 
with potassium iodide, then washed, dried, and 
weighed. No. 1 contains the silver chloride, 
bromide, and iodide. No. 2 contains only silver 
bromide and iodide, the chloride having been by 
this process converted into bromide. No. 3 



contains silver iodide only, the chloride and 
bromide having been both converted into iodide. 
The exact quantities of each in the solution can 
therefore be easily calculated. The valuation of 
commercial iodine has been alluded to already ; 
the sodium thiosulphate is usually standardised 
by titrating it with a potassium iodide solution 
of pure iodine. 100 c.c.=2-48 grams dfeth of 
Na2S20„,5H20) and is equal to 1-27 grams of 
iodine (yjjth of atomic weight in grams). Another 
method of volumetrically estimating the strength 
of an iodine solution is to pass sulphuretted 
hydrogen into it until decolorised; the hy- 
driodic acid formed is then titrated with deci- 
normal soda, using methyl orange as an indicator. 

Commercial iodine seldom contains any im- 
purity but moisture ; it is almost impossible to 
estimate the water by drying in the ordinary 
way. An easy method is to rub it up with 
five times its weight of pure dry mercury, 
adding a little alcohol. It is then dried for 
12 hours, or until it ceases to lose weight, over 
sulphuric acid in a desiccator. This process is 
accurate to about 0-1 p.c, but most suitable for 
very damp iodine. Another method is to add a 
weighed quantity (about double the weight of 
the iodine) of zinc sheet in small pieces in a 
tared capsule, along with a little water, when 
the iodine is all converted into zinc iodide ; the 
contents of the capsule are gradually evaporated 
to dryness and weighed, the weight then includes 
that of the dry iodine. It is better, however, ia 
aU oases to estimate the iodine by titration. The 
same may be said of the valuation of potassium 
iodide ; but in this case it is often also necessary 
to estimate a small quantity of chloride which 
is always present ; and silver nitrate is the best 
reagent for this purpose, as the chloride ought 
to represent so small a percentage as to be di£S- 
cult of detection. Bromine as a rule need not 
be looked for. Should it be present, however, 
some other process must be employed. It is 
necessary to take at least 3 grams of the potas- 
sium iodide, and add to it not less than 3-1 grams 
of pure silver nitrate, the precipitate is digested 
in strong ammonia, then filtered off, washed, 
dried, and fused with the usual precautions. 
The solution is concentrated by evaporation, 
and the silver chloride precipitated by nitric 
acid. This gives accurate results, even when 
the potassium chloride is under 0-5 p.c. 

For the determination of small proportions 
of chlorine and bromine in iodine, the following 
process is recommended by Tatlock and Thom- 
son (J. Soc. Chem. Ind. 1905, 24, 187). 10 grams 
of the sample are triturated with 100 c.o. of 
water, and finely granulated zinc, or zinc dust, 
is added in small portions, with agitation, until 
all the iodine is converted into zinc iodide. The 
temperature of the solution must not be allowed 
to rise sensibly during the process. The solu- 
tion is now filtered, the residue washed two or 
three times, and to the filtrate 7 grams of pure 
sodium nitrite are added. The solution is 
carefully acidified with dilute sulphuric acid, the 
precipitated iodine is collected and washed two 
or three times with cold water, and the filtrate 
is agitated with benzene in a small separator. 
The aqueous layer is run into another small 
separator, mixed with a little more sodium 
nitrite and dilute sulphuric acid, and again 
shaken with benzene. To the aqueous solution 



1S6 



IODINE. 



excess of silrei nitrate and some nitric acid are 
added, the liqnid is heated to boiling, and the 
precipitate is collected on a weighed flltei and 
well washed with hot water. A solution con- 
taining 2 grams of silver nitrate, 90 0.0. of water, 
and 10 0.0. of ammonia of sp.gr. 0-88 is prepared. 
About 60 C.C. of this solution are poured back 
and forward through the filter containing the 
precipitate, and the latter is finally washed with 
the remaining 40 c.c. The silver bromide on the 
filter is now washed with warm dilute nitric acid 
and with hot water, dried, and weighed. The 
ammoniacal filtrate is acidified with dilute nitric 
acid, and the precipitate of silver chloride is 
collected as usual. G. G. H. 

lODIPIN, lODIVAL, lODLECITHIN, v. 
Synthetio dbttos. 

lODOCAFFEIN v. Synthetic dkuqs. 

lODOETHYLFORMIN C,HijN4(CjH5l)j is 
obtained by the action of ethyl iodide on a weak 
alcoholic solution of hezamethylene-tetrainine. 
Crystallises in long needles, tasteless, soluble in 
water, sparingly soluble in alcohol, insoluble in 
ether and chloroform. Decomposed by sodium 
carbonate and strong acids with liberation of 
formaldehyde ; used internally as a substitute 
for alkaline iodide. 

IODOFORM Tri-iodomethane CHIj. Iodoform 
was discovered in 1822 by Serullas (Ann. Chim. 
Phys. [ii.] 20, 165 ; 22, 172 ; 25, 311 ; 29, 225 ; 
39,-230), and Dumas in 1834 {ibid. [ii.]56, 122) 
determined its exact composition. Serullas ob- 
tained it by acting on alcohol with iodine- in 
presence of caustic or carbonated alkalis. The 
reaction may be stated thus : 
CHj-CHj-OH-f 4Ii,-f 6K0H 

=CHIj-t-HCOOK-f5KI-t-5HjO. 
Numerous other compounds have been suggested 
as substitutes for alcohol in this reaction, by 
Serullas, Bouchardat (J. Pharm. Chim. [ii,] 23, 
1 ; [iii.l 3, 18), Lefort (Compt. rend. 23, 229), 
Millon {ibid. 21, 828), and others ; but Lieben 
(Annalen Suppl. 7, 218 and 377) has shown 
that many of these, such as ether, chloroform, 
methyl alcohol, formic and acetic acids, phenol 
and probably the carbohydrates, when properly 
purified, do not yield iodoform. The reaction, 
however, takes place with ethyl ethers, which 
first break up by the action of water into alcohol 
and acid ; with aldehyde, acetone, and generally 
with the higher normal alcohols of the fatty 
series and their corresponding aldehydes ; also 
with lactic acid, turpentine, methyl benzene, 
and some other compounds. This reaction 
serves in many instances as a very delicate 
and reliable test for the presence of alcohol. 
It may be obtained in dilute solutions (Lieben, 
Annalen Suppl. 7, 236). In the reaction with 
turpentine, Guyot (J. Pharm. Chim. [iv.] 13, 313) 
and Chautaud {ibid, [iv.] 14, 19) employ iodated 
lime. When iodine is made to act on sodium 
ethoxide, instead of on alcohol and alkali, 
methylene iodide is formed together with only 
small proportions of iodoform (Butlerow, 
Annalen, 107, 110; Mulder, Eeo. trav. chim. 
7, 310). Iodoform was observed by Erlenmeyer 
(J. 1861, 668) among the products of the action 
of hydriodic acid on glycerol, and Bice (Pharm. 
J. [iii.] 6, 765) notes that a mixture of ' white 
precipitate,' alcohol, and iodine does not explode 
from the formation of nitrogen iodide when phenol 
is present, but that nitrogen and iodoform are 



formed. Iodoform may also be extracted from 
the product of the action of coal gas on iodine 
(Johnston, Phil. Mag. 17, 1). Acetylene mer- 
curic chloride, silver and cuprous acetylides, 
and a solution of acetylene in concentrated 
sulphuric acid all yield iodoform when treated 
with iodine and dilute sodium hydroxide solu- 
tion (Le Comte, J. Pharm. Chim. [vi.] 16, 297). 
To prepare iodoform, MLhol (J. Pharm. Chim. 
[iii.] 7, 267 ) adds 1 part of alcohol to a solution of 
2 parts of crystallised sodium carbonate in 10 
parts of water and raises the temperature to 
60°-80°. 1 part of iodine is then gradually 
added, and when the liquid has become colour- 
less, iodoform slowly forms and sinks to the 
bottom and may be removed by filtration. The 
filtrate is heated as before, another portion of 
sodium carbonate and alcohol added, and chlor- 
ine is led into the mixture to liberate iodine 
which has combined with the alkali. Another 
deposit of iodoform occurs, and the process may 
be repeated until the product represents nearly 
half the iodine employed. Another plan, 
suggested by Bother (Pharm. J. [iii.] 4, 694), is 
to warm the following mixture until it becomes 
colourless : iodine 32 parts, potassium carbonate 
32 parts, 95 p.c. alcohol 16 parts, water 80 parts. 
The iodoform which is deposited is removed, and 
to the clear solution a mixture of potassium di- 
chromate 2 to 3 parts, and hydrochloric acid 16 
to 24 parts, is added, to liberate iodine. After 
neutralising the solution with potassium car- 
bonate, 32 parts more of that salt are added, 
together with 6 parts of iodine and 16 parts of 
alcohol, and the heat being maintained a second 
quantity of iodoform precipitates. This may 
be removed and the operation repeated several 
times (e/. Cornelius and Qille, J. Pharm. Chim. 
[iii.]-22, 196 ; Smith, Pharm. J. [iii.] 6, 211 ; Bell, 
ibid, [iii.] 12, 786 ; Giinther, Arch. Pharm. [iii.] 
25, 373). Iodoform can be prepared by the 
electrolysis of a solution of an iodide in the 
presence of alcohol, aldehyde, or acetone (Dingl. 
poly. J. 255, 88 ; J. Soc. Chem. Ind. 1885, 243 
Foerster and Meyes, J. pr. Chem. [ii.] 66, 363 
Elbs and Herz, Zeitsch. Elektrochem. 4, 113 
Abbot, J. Phys. Chem. 1903, 84; Teeple, Ameri 
Chem. J. 26, 170). According to Suilliot and 
Baynaud (Bull. Soc. chim. [iii.] 1, 3) almost 
the whole of the iodine employed is obtained as 
iodoform when acetone is acted upon by what is 
possibly nascent potassium hypoiodite produced 
by treating potassium iodide with sodium hypo- 
chlorite. A slight excess of dilute solution of 
sodium hypochlorite is added to a mixture of 
potassium iodide 50 parts, acetone 6 parts, and 
sodium hydroxide 2 parts, dissolved in. 1 to 2 
parts of water. The reaction probably takes 
place thus : 

(1) KI-fNaaO=iaO-f Naa. 
(2) CH,-C0-CHa+3KI0 

=CHI,+CH5COOK;-f2KHO. 
This process has been applied to the working of 
kelp, and is said to produce iodoform of a very 
high degree .of purity (Pharm. J. [iii.] 20, 423). 

Iodoform crystallises in lemon-yellow hexa- 
gonal platas (Bammelsberg and Kokscharow, J. 
1857, 431) which melt at 119°, volatilise when 
heated {cf. Dott, Pharm. J. [iii.] 16, 299 ; 17, 282), 
or better in a current of steam. It has a per- 
sistent and disagreeable odour. It is nearly in- 
soluble in water, benzene, or light petroleum, 



lODYRITK 



187 



but dissolves in ether, alcohol, and volatile oils 
(c/. Vulpius, Aroh. Pharm. pii. ] 20, 44). Crystal- 
line form (Pope, Chem. Soo. Traua. 75, 46). 
Lowering of the freezing-point in benzene solu- 
tion (Paternb, Ber. 22, 465). In the dry state 
iodoform is not acted on by sunlight; but in 
solution, with access of oxygen, it rapidly 
liberates free iodine (Humbert, J. Pharm. Chim. 
[iii.] 29, 352 ; Hebeler, Pharm. J. [iii.] 16, 1088; 
Daocomo, Gazz. ohim. ital. 16, 247 ; Neuss and 
Schmidt, Pharm. J. [iii.] 19, 247 ; Fischer, Pharm. 
Zeit. 34, 31 ; Bougault, J. Pharm. Chim. [vi.] 8, 
213). Iodoform has been much used in medicine 
and surgery as an antiseptic, but its value in this 
respect has often been questioned. It would ap- 
pear, however, that while outside the system it 
exerts no antiseptic power, it acts differently in 
presence of pus at the temperature of the body. 
Iodine is, in this case, liberated which combines 
with ptomaines to render them innocuous (De 
Ruyter, Med. Press Cir. 1887, 403 ; c/. Riedlin, 
Arch. Hygiene, 7, 309, and Ber. 22, Ref. 66; 
also Altenberg, Chem. Zentr. 1901, ii. 1212; 
Mulzer, ibid. 1905, i. 1174). Numerous at- 
tempts have been made to mask the odour of 
iodoform in its pharmaceutical preparations 
(Pharm. J. [iii.] 8, 439; 11, 111 and 895 ; 12, 439 
and 703; 16,288; 17,556; 18,249). For iodo- 
form gauze V. Daux, J. Pharm. Chim. [5] 16, 201. 
When iodoform is heated in closed tubes to 
150°, methylene iodide is formed (Hofmann, 
Chem. Soc. Trans. 13, 65). The zino-copper 
couple reduces it to acetylene (Gladstone and 
Tribe, ibid. 28, 512). Bromine converts it 
into bromoform (Loscher, Ber. 21, 410), and 
phosphorus pentachloride into chloroform. 
Finely divided silver, even in the cold, 
reduces iodoform, acetylene i^nd eUver iodide 
being formed. Other metals act in the same 
way, but in the case of iron in the presence of 
water the products are methyl and methylene 
iodides (Cazeneuve, Compt. rend. 97, 1371 ; 98, 
369). With sodium ethoxide, methylene iodide, 
acrylic acid, and ethyl lactic acid are produced 
(Butlerow, Annalen, 107, 110; 114, 204; 118, 
325). Methylene iodide is also formed by the 
action of potassium hydroxide on a solution of 
iodoform in acetone (Willgerodt and MuUer, 
Chem. Zentr. 1884, 808). Iodoform reacts with 
certain mercury and silver salts. Mercuric 
acetate is reduced to mercurous acetate with 
evolution of carbon dioxide (Cotton, J. Pharm. 
Chim. [v.] 16, 481) ; mercurous chloride is con- 
verted into mercurous iodide and chloroform 
(Brescher, Pharm. J. [iii.] 17, 882), the reaction 
being similar to that between iodoform and 
phosphorus pentachloride; and dry silver 
nitrate is decomposed with explosive violence, 
silver iodide, nitrogen peroxide, nitric acid, and 
carbonic acid being probably formed (Pharm. J. 
[iii.] 20, 62). The last-mentioned reaction has 
been made the basis of a method for the volu- 
metric estimation of iodoform (Greshoff, Rec. 
trav. ohim. 7, 342). A crystalline but unstable 
compound of Iodoform with strychnine is 
described by Lextrait (Compt. rend. 92, 1057). 
A reaction, which has been employed as a test, 
is obtained when a few drops of an alcoholic 
solution of iodoform are added to a smaJl 
quantity of a mixture of phenol and solution of 
caustic potash, and the mixture gently warmed. 
A red precipitate is formed which, dissolved in 



a small quantity of alcohol, exhibits a carmine 
red colour (Lustgarten, Monatsh. 3, 717). Detec- 
tion of adulteration (Kremel, Ph. Post, 21, 213). 
Assay of iodoform (MeiUfere, Chem. Zentr. 1898, 
ii. 140). A. S. 

lODOFORMAL v. Synthbtio detjgs. 

lODOFORMIN OnHjjNJi is prepared by 
adding an alcoholic solution of iodine to ammonia 
and formaldehyde mixed in molecular propor- 
tions when iodoformin falls as a brown pulveru- 
lent precipitate («. Synthetic dettos). 

lODOFORMOGEN v. Synthetio dbtjgs. 

lODOKOL V. Synthetic dbtjbs. 

lODOLE Tetraiodopyrrole CJiNH. lodole is 
an antiseptic, similar in its action to iodoform. 
It is less energetic, but is free from the dis- 
agreeable smell which characterises that com- 
pound. References to communications on the 
physiological action of iodole and its application 
in therapeutics are given by Ciamioian (Gazz. 
chim. ital. 16, 643). Cf. Trousseau (Pharm. J. 
[iii.] 17,265); and Robinson (Chem. Zeit. 1887, 
222). 

Gamician and Dennstedt, who first prepared 
iodole, obtained it by acting on potassium pyrrole, 
CjHjNK,"with iodine in ethereal solution (Ber. 
16, 2582): It is formed, even in the cold, when 
iodine is brought in contact with pyrrole, 
in presence of such indifferent solvents as 
alcohol, wood spirit, chloroform, acetone, carbon 
disulphide, or ethyl acetate. The reaction may 
beexplainedthus:C4H4NH+8I=C4liNH+4HI. 
It is, however, better to add some agent to re- 
move the hydriodic acid as it is formed, such 
as alkalis or their carbonates ; or to oxidise it 
with such substances as ferric chloride, cupric 
sulphate, chlorine or bromine, oxide of man- 
ganese, &o., and thereby utilise the whole of 
the iodine (Ciamician and Silber, Ber. 18, 1766, 
19, Ref. 327). lodole may also be obtaineid from 
the corresponding chlorine or bromine deriva- 
tives of pyrrole by the action of metaUio 
iodides (Patent, Ber. 20, Ref. 123). 

lodole crystallises from alcohol in light yellow 
microscopic needles. Heated at 140°-150° it de- 
composes without melting. It is insoluble in 
water but easily dissolves in ether, in hot 
alcohol or glacial acetic acid, or in alcoholic 
pptash. The alcoholic solution with nitric acid 
gives an intense red colour, and a green colour 
is obtained when the crystals are heated with 
sulphuric acid. Acted upon by zinc-dust and 
potassium hydroxide, iodole is converted into 
pyrrole (Ciamician and Silber, Ber. 19, 3027) (v. 
Synthetic drugs). A. S. 

lODOLEN, lODOLIN, lODOGALLICIN, 
lODOFHEION, lODOTHTRINS, lODOZOL, v. 
Synthetic dbugs. 

lODOMENIN V. Synthetic dbtjos. 

IODOMETRY v. Analysis, Volumbteio. 

lODOPYRINE. A pharmaceutical prepara- 
tion made by adding a solution of iodine in 
potassium iodide to an aqueous solution of 
antipyrine containing sodium acetate. 

lODOTHEOBROMlN, lODOTHYRIN, lODY- 
LIN, lODYLOFORM, v. Synthetic DsirGS. 

lODOTHlON V. Synthetic detjgs. 

lODYRITE, or lodargyrite. A mineral com- 
posed of silver iodide (Agl) crystallising in the 
rhombohedral system. Distinctly developed 
crystals are small and comparatively rare ; they 
possess a perfect cleavage parallel to the basal 



158 



lODYEITE. 



plane, on whish the lustre ia pearly, aud are 
very soft (H.= 1) and readily distorted. Their 
pale sulphur-yellow is not darkened by ex- 
posure to sunlight. Sp.gr. 5'61. At a tem- 
perature of 146°, the material becomes optically 
isotropic and cubic, reverting on cooling into 
the birefringent rhombohedral form. 

The mineral occurs in the upper oxidised 
zones of certain silver-bearing veins, and when 
found in quantity, as at Broken Hill in New 
South Wales, in Chile and Mesco, it is an im- 
portant ore of silver (Ag, 45-97 p.c). Some of 
the silver-ore formerly mined at Broken HiU 
consisted of white kaolin enclosing films and 
specks of iodyrite. 

Miersite is a rare cubic form of silver iodide 
with copper iodide (4AgI-CuI) from Broken HiU, 
New South Wales (L. J. Spencer, Min. Mag. 1901, 
. 13, 41 ; G. T. Prior, I.e. 188). L. J. S. 

IONIUM. A radioactive element, discovered 
by Boltwood in uranium minerals (Boltwood, 
Amer. J. Sci. 1907, 24, 370 ; cf. Hahn, Ber. 1907, 
40, 4415). The results obtained by Boltwood and 
Hahn were co«firmed by Marckwald and Keet- 
man (Ber. 1908, 41, 49), who were unable to 
separate ionium from thorium, an element which 
it closely resembles. Ionium occurs, however, 
associated with actinium, in many of the uran- 
ium group of minerals in the absence of thorium 
(SzilArd, Le Radium, 1909, 6, 80). 

Highly active preparations of ionium may 
be obtained from carnotite as follows (Boltwood, 
Amer. J. Sci. 1908, 25, 365). The ore is dis- 
solved in hydrochloric acid and several grams 
of the chlorides of the cerite earths added The 
earths are separated as oxalates, converted Into 
chlorides, and precipitated with sodmm thio- 
sulphate. The latter procedure is repeated 
several times, when a product ia obtained 
having a radioactivity sereral thousand times 
as great as that of an equal weight of pure 
uranium. 

The residues obtained in working up uranium 
ores containing little thorium may be precipi- 
tated in strongly acid solution with hydrofluoric 
acid. The precipitated fluorides are converted 
into sulphates, and from the aqueous solution 
of these, ionium and thorium are quantitatively 
precipitated by adding zinc hydroxide. The 
precipitate is cfissolved in hydrochloric acid and 
the solution precipitated with oxalic acid. The 
oxalate thus obtained contains the ionium, and 
has an activity 200 times as large as that of 
metallic uranium (Keetman, Jahrb. Badioaktiv. 
Elektronik. 1909, 6, 265). 

Ionium emits c-rays, which have a range in 
air of only 2-8 cms. ; it also emits ;8-rays. It 
produces no emanation. The life of ionium is 
at least as long as that of radium. 

According to Boltwood, ionium is the direct 
parent of radium, and according to Keet- 
man (2.C.), does not change directly into 
actinium. 

Thorium-ionium oxalate has a very high 
and constant activity, and may with advantage 
be utilised in testing the constancy of electro- 
meters and for determining capacities (Keet- 
man. I.e.). 

lONONES V. Ketombs. 

IPECACUANHA. IpeeacuanJui Root. Racine 
d' Ipfcacitanka, Pr. ; Brechwurzd, Get. Ipe- 
cacuanha occurs in commerce as a dusky grey 



root, with a thick bark, transversely corrugated 
or ringed, the corrugations often penetrating to 
the woody interior, and minutely wrinkled longi- 
tudinally. The root attains a diameter in some 
cases of ^ to ^ of an inch, and as many as 
twenty rings may be counted to the inch in 
length. It has a short friable, not fibrous, frac- 
ture, and the bark, which constitutes some three- 
fourths of the root, separates easily from the 
wood. (Cf. Fluck. a. Hanb. 373 ; Tschirch and 
Ludtke, Arch. Pharm. 1888, 432.) 

The drug was first introduced into Europe 
from Brazil about the close of the 17th century 
as a remedy for dysentery, and since that period 
it has always retained a place among articles of 
materia mediea. Its employment has, how- 
ever, been mainly as an expectorant and emetic, 
but it has frequently been used in the treatment 
of intestinal diseases, and its historic reputation 
as a remedy for dysentery has been somewhat 
revived in India. Applied locally the powdered 
root is an irritant, and in large doses it is poison- 
ous. {Cf. Pereira, Mat. Med. 1833, 2, 1591 ; Fliick. 
a. Hanb. 370.) It is administered either in 
the state of powder — for instance, admixed with 
opium and potassium sulphate in the well-known 
Dover's Powder — or made into piUs, or in vinous 
solution. The mode of preparation of the drug 
for use in medicine has been much studied by 
pharmacists (v. indexes Ph. and Year-Bk. Ph.). 

The root is derived from the Uragoga Jpeea- 
cuariha [Willd. (Baill.)], a low shrub found for 
the most part between 8° and 22° S. latitude, in 
Brazil and also to some extent in the adjoining 
portions of New Granada and Bolivia. The 
plant grows in shady forests, in valleys, but not 
actually in swamps. According to Balfour the 
plant exists in two varieties, one having a woody 
and the other an herbaceous stem (cf. Bentl. 
a. Trim. 145 ; Fluck. a. Hanb. 374 ; Pockling- 
ton, Pharm. J. [iii.] 2, 841, 921). 

The most important constituent of ipeca- 
cuanha is the alkaloid emetine, first obtained in 
an impure state by Pelletier and Magendie in 
1817 (Ann. Chim. Phys. [ii.] 4, 172), and further 
studied by Pelletier (J. Pharm. Chim. [ii.] 3, 145 ; 
14, 200), Pelletier and Dumas (Aim. Chim. 
Phys. [2] 24, 180), Merck (Neues Jour. Tromms- 
dorf. 20, 1, 134), Buchner (Rep. Pharm. 7, 
289), Landerer (iUi. 52, 211), Reich (Arch. 
Pharm. [2] 113, 193), Lefort (J. Pharm. Chim. 
[iv.] 9, 241), Pander (J. 1871, 373), Gle'nard 
(J. Pharm. Chim. 22, 178; Compt. rend. 81, 
100), Lefort and F. Wurtz (ibid. 84, 1299), 
Power (Pharm. J. [iii.] 8, 344), Kunz-Krause 
(Arch. Pharm. [3] 25, 461; 232, 466) and 
Podwjssotzky(Pharm. J. [iii.] 10, 642); Kremel 
(Arch. Pharm. [iii.] 26, 419). 

The emetine of the earlier investigators has 
been shown by Paul aud Cownley (Pharm. J. 53, 
61 ; [iii.] 25, 111) to be a mixture of at least two 
different alkaloids ; one, a base insoluble in 
caustic alkalis, for which it is proposed to retain 
the name of emetine ; the other, cephmline, is 
soluble in caustic alkalis. These were separated 
from ipecacuanha by extraction with alcohol, 
precipitation with basic lead acetate, evapora- 
tion of the filtrate to dryness, and treatment of 
the residue with dilute acid ; the solution wa& 
mixed with ether, ammonia added in slight 
excess, and shaken, and from the separated 
ethereal solution, dilute sulphuric acid took up 



IRIDIUM, 

the emetine, which was precipitated by adding 
oaustio soda solution and treated further in 
order to entirely remove the other base. The 
alkaline solution when acidified and then shaken 
with ether and ammonia yielded oephseline. 
Emetine CijHjsNOj melts at 68°, is amorphous, 
strongly alkaline and colourless, but turns yellow 
when exposed to light. It is soluble in alcohol, 
ether, chloroform, or benzene, but only spar- 
ingly so in hot light petroleum or in water. 
Cephaeline CnH^aNOa is colourless, but, like 
emetine, is turned yellow by exposure to light. 
It is less soluble in ether than emetine. It 
melts at 119° when all the solvent has been 
driven off (Frerichs and Tapis, Arch. Pharm. 
240, 390). 

A third alkaloid, psycJiotrine, has been iso- 
lated from ipecacuanha (Paul and Cownley, 
Pharm. J. [iii.] 25, 690). It exists in relatively 
small proportion, is characterised by its very 
sparing solubility in ether, and remains in the 
ammoniacal liquor from which emetine and 
cephaehne have been extracted by ether. 
Psyohotrine forms pale yellow crystals which 
mdt at about 138°. The proportions of these 
alkaloids in Brazilian, Columbian, and Indian 
ipecacuanha are given by Paul and Cownley 
(Pharm. J. [iv.] 2, 321 ; 15, 256). Allen and 
Soott-Smith (Analyst, 27, 345) give a table 
comparing the colour reactions of emetine, 
cephseline, and psyohotrine. 

To determine the value of ipecacuanha or its 
pharmaceutical preparations, an estimation of 
the alkaloidal content is made. This is done 
either by a process similar to one of those given 
for the extraction of the alkaloid («. Kremel, 
Pharm. Post, 21, 151) or, having obtained a suit- 
able solution, by titration with Mayer's reagent 
{cf. Zinoffsky, Pharm. J. [iii.] 3, 342 ; Bragen- 
dorff, Werthbestimmung einiger starkwirkender 
Droguen, 1874, 37 ; Stewart, Amer. J. Pharm. 
1876, 359; Naylor, Pharm. J. [iii.] 16, 607; 
Lyons, ibid, [iii.] 16, 627 ; Zeitsch. anal. Chem. 
28, 258; Fliiokiger, Pharm. J. [iii.] 16, 643; 
Jones, ibid, [iii.] 17, 277 ; Alcock, ibid, [iii.] 16, 
680; Ransom, ibid, [iii.] 18, 241, 400; Cripps 
and Whitby, ibid, [iii.] 19, 721 ; Braithwaite and 
J. C. Umney, ibid, [iii.] 20, 252, 253 ; Arndt, 
Pharm. Zeit. 1889, 685 ; KoEer, Chem. Zentr. 
1893, i. 235, 322 ; 1894, i. 236 ; J. Pharm. Chim. 
[v.] 27, 465 ; Frerichs and Tapis, Arch. Pharm. 
240, 390). 

Besides emetine, ipecacuanha contains a com- 
pound ipeeaciianhic acid Ci,!!^©, (WiUigt, Sitz. 
Ber. K. Akad. Wien. 5, 192) which was thought 
by Pelletier (Ann. QJum- Phys. [ii.] 4, 172) to be 
gaUic acid. It is a reddish-brown amorphous 
mass, with a bitter taste and very hygroscopic. 
It is soluble in water or alcohol, but less so in 
ether. With ferric chloride it gives a green coloxu:. 
It reduces salts of silver and mercury, and is not 
precipitated by neutral lead acetate. Kunz 
round the root to contain choline. The colouring 
matter of ipecacuanha was examined by Pod- 
wyssotzky. It forms purple-red compounds 
with alkalis. From its combination with 
barium an acid was obtained, erythrocephalein, 
which crystallises from chloroform in straw- 
coloured needles. When the root is distilled 
with sodium carbonate and a little ferric chloride, 
a distillate is obtained from which a crystalline 
fluorescent volatile aVcahid may be isolated 



1S9 

(Arndt, Chem. Zentr. 1889, 43^; Pharm. Zeit. 
1889, 585). It is present to the extent of 0-3 p.c. 
It forms compounds with most alkaloidal re- 
a.gents, and gives a hydrochloride which crystal- 
lises in fluorescent octahedrons. No trace of 
this volatile alltaloid, however, could be found 
by Cripps (Pharm. J. [iv.] i. 169). Ipecacuanha 
also contains gum (WiJIigt), starch, 30 p.c. in the 
cortica and 7 p.c. in the woody portion (Fliick. 
a. Hanb. ), and other constituents usually found 
in plants. It yields about 3 p.c. of ash (Mummg, 
Pharm. J. [iii.] 17, 898). 

For characters of allied plants, such as 
striated ipecacuanha, Psychotria emetica (Linn.), 
and undulated ipecacuanha, Bichardsonia grandi- 
flora (Cham, et Sohlecht.), and others sometimes 
substituted for Uragoga, cf. Fliick. a. Hanb. 375 ; 
Attfield (Pharm. J. [ii.] 11, 140) ; Planchon (J. 
Pharm. Chim. [iv.] 16, 404; 17, 19); Power 
(Pharm. J. [iii.] 8, 344) ; Kirkby {ibid, [iii.] 16, 
126) ; Hooper {ibid, [iii.] 18, 317) ; and Ransom 
{ibid, [iii.] 18, 787). A. S. 

IRETOL V. Phenol and its homoloqxjes. 

IRIDIN V. GurcosiDES. 

IRIDIUM. Sym. Ir. At.wt. 193-1. 

The occurrence of this metal and the proper- 
ties of its principal alloys with platinum will 
be described under Platinum. Its principal 
source is the osmiridium which is left after 
treatment of crude platinum with aqua regia. 

The osmiridium is first freed from sand and 
certain other admixed metals by lixiviation 
with water, after which it is brought into a fine 
state of division by melting it with its own 
weight of lead, and once or twice its own weight 
of oxide of lead. The mixture is kept at red 
heat for half an hour, treated successively with 
nitric acid, and with aqua regia, and then sifted 
through fine silk. The division of the mineral 
may also be brought about by melting it with 
zinc and then removing the latter by means of 
hydrochloric acid or by volatilisation. 

The finely-divided mineral may now be 
fused with barium or sodium peroxide, with 
sodium chloride, or with » mixture of nitre and 
potash, after which the mass is taken up with 
water containing alcohol, then with hydrochloric 
acid which converts the metals into chlorides. 
These are transformed into double chlorides by 
the potassium chloride, and the metals are 
finally separated as nitrites. 

The solution of the chlorides, after standing 
for 24 hours, is filtered, and the filtrate treated 
with sodium nitrite, iron is precipitated as 
sesquioxide and gold (if present) as metal ; on 
addition of soda any remaining lead, copper, and 
bismuth are precipitated. The solution is now 
made alkaline with soda and treated with 
chlorine at 60°-60'', whereby osmium and 
ruthenium oxides are volatilised. The residue is 
acidified with hydrochloric acid, and the iridium 
and rhodium are precipitated as ammonium 
double nitrites by means of sodium nitrite and 
ammonium chloride. The precipitate is fil- 
tered off, dissolved in warm hydrochloric acid, 
and again treated with ammonium chloride, 
whereupon iridium separates as ammonium 
icidochloride, whilst the rhodium remains in 
solution (Deville and Debray, Compt. rend. 1874, 
78, 1502; Leidi6, ibid. 1899, 129, 214; ibid. 
1900, 131, 888; Quenessen, ibid, 1905, 141, 



160 



IRIDIUM. 



258 ; Leidi6, BuU. Soo. ohim. 1901, [iu.] 26, 9 ; 
ibid. 1902, [iii.] 27, 179; ibid. 1903, [iii.] 29, 
801 ; Gibba, J. pr. Chem. 1864, 91, 175). 

The mineial may also be fused with potash 
and potassium chlorate ; on treating the mass 
with water, the osmium and ruthenium are 
dissolved, whilst the iridium mixed with some 
platinum lemains as a blue-black powder, 
which is attacked by acids, and from which 
the platinum may be removed by means of 
sulphuretted hydrogen, the iridium remaining 
behind as a sesquichloride. 

Iridium may be separated from gold by heat- 
ing the mixture in a clay crucible. The fused 
gold is poured o£E and the iridium silicate 
remaining is reduced (MietzschM, J. Fharm. 
CShim. 1902, 15, 68). 

The metal, may be isolated by heating 
iridium ammonium chloride with reducing 
agents at a dull red heat (U.S. Fat. 805316, 
1905). 

.Mother method of separating- iridium 
sometimes employed, is to mix the finely-divided 
osmiridium with sodium chloride in a porcelain 
tube and pass a current of chlorine through it. 
This converts the metals into chloride, and the 
iridium can then be separated by means of 
sulphuretted hydrogen (Schneider, Annalen, 
.1867, Suppl. 6, 267). 

On accotmt of their extreme hardness, the 
native grains of osmiridium are employed as 
such for tipping the points of gold nibs, but 
only a small proportion even of the few grains 
which occur with ordinary crude platinum are 
suitable for the purpose. A small quantity of 
osmiridium is used for pivots, &c., of watches 
and scientific instruments, but practically the 
whole is worked up for the production of iridium, 
which is mainly employed in alloy with platinum 
for the manufacture of crucibles and for many 
other purposes. Owing to its extreme hardness 
and to its power of retaining its temper and 
edge under conditions where steel requires 
constant sharpening, iridium has been employed 
in preference to that metal, for wire-drawing, 
jewellers' tools, points for compasses and 
watches, and for edging cutters for rubber, 
celluloid, &c. If the metal could be produced 
in quantity, it would find extended use in place 
of platinum forcnicibles. Such crucibles possess 
the hardness of steel and show no alteration in 
weight on strong ignition, although they become 
bluish at a red heat from superficial oxidation, 
which disappears on stronger heating. With 
a badly regulated gas flame, a deposit of carbon 
is produced upon the crucible, but this readily 
bums o£E and leaves no ill effect as regar(js 
weight, appearance, or brittleness. Boiling with 
aqua regia, fusion of phosphates in presence of 
carbon, the heating of silica or silicates with a 
reducing agent, or even fusion of metallic 
lead or zinc in the crucibles, is without apparent 
action. Prolonged fusion of copper in iridium 
makes it brittle when hot, but if the heat be 
raised sufficiently to volatilise the copper, the 
iridium shows no ill effect. 

Iridium is a white metal as bright as steel, 
having a sp.gr. of 22-39 (G. Matthey), and 
melting at about 1950° ; 2160°-2250° (J. Ind. 
Eng. CJhem. 1911, 3, 354). 

Under ordinary conditions, iridium is not 
attacked by any acid, not even by ogito regia. 



At a dull red heat it combines with fluorine, 
chlorine, or oxygen. It also combines with 
sulphur when heated, and gives a readily fusible 
compound with phosphorus, which is decom- 
posed at a white heat. 

Colloidal iridium may- be obtained by mixing 
iridium chloride with lysalbio acid and con- 
centrated soda, and subsequently dialysing the 
mixture (Faal and Amberger, Ber. 1904, 37, 
124); or by reducing iridium chloride with 
hydrazine hydrate in the presence of gum arable 
solution (Gutbier and Hoffmeier, J. pr. Chem. 
1905, [ii.] 71, 452). It is a catalyst, but is not as 
powerful as colloidal platinum. 

Iridium blach is a complex mixture containing 
varying proportions of the metal and its oxides, 
obtained by reducing iridium salts with alcohol, 
formic acid, or formaldehyde. The black 
powder thus formed is washed with water and 
dried in vaeuS (Bottger, J. pr. Chem. 1834, 3, 
276). 

It has properties similar to, but more power- 
ful than, those of platinum black. It absorbs 
gases and has the property of inducing chemical 
action, as, for instance, the combustion of 
hydrogen and of alcohol, the transformation of 
chlorine, iodine, or bromine water into halogen 
acid and oxygen, the decomposition of hypo- 
chlorites, and so forth (Schonbein, Ann. (3am. 
Fhys. 1866, [iv.] 7, 103, 113). It dissolves in 
aqua regia, as does also iridium in alloy with 
platinum. 

Although the black iridium oxide is a valued 
pigment for china, the commercial use of 
iridium for that or other purposes other than 
as metal or in alloys, is practically nil, as the 
demand for the metal as such exceeds the 
supply. For the same reiason, none of the large 
variety of salts which iridium forms, are of 
technological interest. 

iBISnrM COMPOTOBS. 

According to Wohler and Witzmann (Zeitsoh 
anorg. Chem. 1908, 67, 323; see also Zeitsch. 
Elektrochem. 1908, 14, 97), the oxide IrO does 
not exist under ordinary conditions. 

Iridittin dioxide IrO, is best prepared by the 
action of alkali on a hot solution of sodium 
iridichloride Na^IrCl,, the sesquioxide first 
formed being oxidised to dioxide by a current 
of oxygen. The oxide is then dried in a current 
of carbon dioxide at 200°, after which it is 
boiled with alkali and then with sulphuric acid. 
The anhydrous dioxide and also the one con- 
taining 2 mols. HjO is black. When freshly 
precipitated it is more readily soluble in acid!s 
and alkalis iiian when dried. 

The solution obtained by the action of 
potash or sodium iridichloride in the cold, 
ultimately becomes violet in colour and contains 
the dioxide in colloidal form ; after a time a 
violet modification of the dioxide separates, and 
on boiling, the solution becomes blue. The blue 
and green solutions of the dioxide in hydrochloric 
acid also contain the dioxide in colloidal 
solution. 

_ Iiidiam sesquioxide Ir,Oj is obtained by 
mixing air-free hot solutions of sodium iridium 
sesquichloride Ir2Cl(,6NaCl,24H20, and potash 
in a current of carbon dioxide. The mixture is 
evaporated to dryness and heated to redness in 
a current of the same gas, after which it is 



lEON. 



161 



purified in tlie same way aa tlie dioxide. With 
hydioohloiio aoid this oxide also gives a colloidal 
solution. Like the dioxide, its piopeities 
depend on the proportion of water it contains. 
The sesquiozide imparts a fine black colour to 
porcelain a/ter firing, and when mixed with 
zinc oxide it yields a grey tint. 

Iridium trioxide is so unstable that it has 
not been obtained pure, 

Itldiom tiihydroxlde Ir(OH), is a yellowiah- 
green substance which dissolves in alkalis and 
oxidises rapidly in the air, forming 

Iridium tetrahydroxide Ir(0H)4, a heavy 
indigo blue powder, which becomes green, then 
brown on heating (Joly and Leidid, Compt. 
rend. 1895, 120, 1341; Gutbier and Riess, 
Ber. 1909, 42, 3905). 

Irldous chloride IrClj is a green, insoluble 
mass, formed when chloruie is passed over 
spongy iridium or when the tetrachloride is 
heated. 

Iridium trichloride IrCl, is a light, insoluble, 
olive-green powder prepared by heating one of 
its double salts with sulphuric acid, and also 
by other methods (Antony, Gazz. chim. ital. 
1893, 23, i. 184). It forms complex compounds 
with the chlorides of phosphorus and arsenic 
(Geisenheimer, Compt. rend. 1890, 110, 1004, 
1336), and double salts with metallic chlorides of 
the type M3lrCl,9HjO. 

Iridium tetrachloride IrCIj may be obtained 
by heating ammonium iridichloride in chlorine, 
or by dissolving the finely-divided metal in 
aqua regia, or the blue hydroxide in hydro- 
chloric acid. It forms double chlorides of 
the type M^IrCI, and with all^l amines 
(Bimbaoh and Korten, Zeitsch. anorg. Chem. 
1907, 62, 406; DelApine, Compt. rend. 1909, 
149, 1072; ibid. 1908, 146, 1267; V&es, 
ibid. 1392 ; Gutbier, Zeitsch. physikal. Chem. 
1909, 69, 304 ; Gutbier and Biess, l.c.). The 
iridichlorides, when reduced, yield the iridio- 
chlorides. Similar bromides and iodides of 
iridium also exist. 

Iridium forms ammonium or ammine deriva- 
tives similar in constitution to the platinum 
compounds and corresponding to the chlorides 
IrClg, Ird^ ; also a series of compounds corre- 
sponding to IrCls, and antilogous to the cobaltic, 
chromic, and rhodic compounds, thus : 

When iridium chloride is treated with 
ammonia, double salts Ir(NHg)3Cl3, 

Ir(NH3)4,Cl3,HjO, 
and Ir(NHj)5Cls,H,0 are formed. Iridium 
ammonia ohiorohydroxide, sulphate, thionate, 
oxalate, nitrate, and a number of halide deriva- 
tives are also known (Falmaer, Zeitsch. anorg. 
Chem. 1895, 10, 320 ; ibid. 1896, 13, 2ll ; see 
also Mylius and Dietz, Ber. 1898, 31, 3187). 

Complex iridium . nitrites and their cliloro 
and oxalic acid derivatives have been prepared 
(Joly and Leidi6, Compt. rend. 1895, 120, 1341 ; 
Leidi«, ibid. 1902. 134, 1582 ; Bull. Soc. chim. 
1902, [iii.] 27, 936; Vfizes and Dtffour, ibid. 
' 1910, [iv.] 7, 507, 512 ; Miolati and Gialdini, 
Atti. R. Accad. Lincei, 1902, [v.] 11, ii. 151 ; 
Werner and Vries, Annalen, 1908, 364, 77). 

Irldicyanldes resemble the ferrioyanides and 
are described by Martins {ibid. 1861, 117, 357 ; 
see also Bimbach and Korten, Zeitsch. anorg. 
Chem. 1907, 52, 406). 
Vol. III.— T, 



Iridium sulphides IrS, Ir^S,, IrS, (Antony, 
Gazz. chim. ital. 1893, 23, i. 184, 190), and the 
ammonium pentadecasulphide (NHt)3lrS|| (Hof- 
mann and Hochtlen, Ber. 1904, 37, 245) are 
known. 

Iridium sulphate ^(SO,), is a yellow-brown 
mass which when warmed with sulphuric acid 
is reduced, giving a green solution of the sesqui- 
sulphate ^^(SO j3,6HjO (Bimbach and Korten, 
I.e.). 

Iridium sesquisulphate fo.rms alums with 
ammonium, thallium, and the alkali metals, of 
the type Irj(S04)3-MaS04,24HjO(M;arino, Zeitsch. 
anorg. Chem. 1904, 42, 213 i Bimbach and 
Korten, l.c. ; DelSpine, Compt. rend. 1906, 142, 
631). It also forms sulphates of the type 

Ir(S04M')3,H20 (?) or Irj(SOi)3-3M2S04,HjO 
which are bluish-green in colour, and are 
decomposed by ammonia and alkali hydroxides 
with precipitation of a violet oxide of iridium. 
The contained sulphuric acid is not precipitated 
by barium (DelSpine, Compt. rend. 1906, 142, 
1525). 

According to DelSpine iridium forms two 
series of disulphates : (1) green salts, generally 
acidic, derived from the acid 

H,[Ir(S04)3(OH)HjO]; 
(2) reddish-brown basic salts derived from the 
acid H,[Ir(S04)3(0H),] (Compt. rend. 1909, 149, 
785). 

He has also obtained green pyridine deriva- 
tives (ibid. 1910, 161, 878). 

Double salts of iridous suVphite have been 
described by Seubert (Ber. 1898, 11, 1761). 

Iridium selenide (Chabrid and Bouchonnet, 
Compt. rend. 1903, 137, 1069) ; oxalates (Gial- 
dini, Atti. R. Acoad. Lincei, 1907, [v.] 16, ii. 
661, 648 ; V6zes and Duffour, Bull. Soc. chim. 
1907, [iv.] 5, 869, 872) ; phosphor halides (Streoker 
and Schurigin, Ber. 1909, 42, 1768) ; and 
mercaptide (Hofmann and Babe, Zeitsch. anorg. 
Chem. 1897, 14, 293) are known. 

IRIS BLUE V. OxAzmE coLOtrRiiro mattebs. 

IRIS GREEN. Sap Oreen (v. Fiqmehts). 

IRISH MOSS GUM v. Gttms. 

IRON. Sym.Fe. At. wt. 55-84. History.— lion 
has been known and prized from the very earliest 
historical period, articles of the metal having 
been found among the contents of the Great 
Pryamid of Egypt, where they are believed to 
have remained for 6000 years. Iron was also 
used in Nineveh in considerable quantities, and 
in the British Museum are picks, hammers, and 
saws made of iron, found by Layard in the ruins 
of Nineveh, and which are believed to be of a date 
not later than 880 B.o. Iron is frequently men- 
tioned in the earlier books of the Bible ; it was 
much prized by the Greeks, and was discovered 
by Sohliomann in the ruins of Mycenie, which 
was "destroyed b.o. 661. The Chinese were ac- 
quainted with the use of iron at a very early 
period, and it was also highly valued and much 
worked by the Bomans. The metal employed 
in all the above instances was obtained by direct 
reduction from the ore, by methods very closely 
resembling those still in use by semi-barbarous 
peoples in various parts of the world. In Eng- 
land iron was largely worked by the Bomans, 
and in the Forest of Dean there are stiU to be 
seen remains of these old Boman workings, 
whilstthe partly reduced slags left by the Bomans 

M 



162 



IRON. 



were in more modem times employed for many 
years in the blast furnaces of that district 
as a source of iron. At the Norman invasion 
Gloucester possessed a considerable trade in 
iron, but until the introduction of coal Sussex 
was the chief seat of the manufacture in this 
country. The exact date at which the blast 
furnace was introduced is not known, and it was 
probably the result of a gradual development of 
the more primitive hearths formerly in use. 
Cast iron was, however, known to Agrioola, who 
died in 1655, and it was employed for cannon in 
this country in the year 1516. At this period 
small blast furnaces were employed which were 
capable of producing about 7-10 tons of metal 
per week, the fuel used being charcoal. The 
resulting pig iron was afterwards converted 
into wrought iron in a finery, or small hearth, 
not nnhke the smith's fire. The large quantities 
of wood employed for the production of charcoal 
for this manufacture led to the introduction of 
various Acts of Farhament during the 16th 
century, which had for their object the restric- 
tion of the industry to certain districts, and a 
diminution of the waste of valuable timber. In 
the early part of the 17th century Dud Dudley 
succeeded in ' charring ' coal or producing a coke 
suitable for use in the blast furnace, but the use 
of coal did not become general until after 
Abraham Darby had again succeeded in the 
manufacture of coke at Colebrook Dale about 
1730. The introduction of the steam engine by 
Watt led to the use of more powerful blowing 
machinery,' and gave increased yields, which 
again were much improved upon by the apphca- 
tion of hot blast in 1829, by subsequent altera- 
tion in the shape of the interior, and by the 
considerable increase in the size and the capacity 
of the furnaces. Various other improvements 
have from time to time been adopted, such as 
the utilisation of the gases from the furnace, 
the use of regenerative hot blast stoves, and the 
introduction of improved methods of calcining 
the ore, so that the present output of the best 
furnaces is about 400 times that of the blast 
furnaces of 200 years ago, whilst the consumption 
of fuel has been reduced to about one-fifth of 
that formerly employed. In connection with 
the manufacture of steel, the cementation process 
is in various forms of very great antiquity, but 
a notable improvement was effected by Hunts- 
man, about 1740, by the introduction of cast 
steel, while a further advance was made in 
1839, when Heath introduced the use of manga- 
nese in steel melting. As before mentioned, 
wrought iron was originally prepared directly 
from the ore, and at a subsequent date was 
obtained from cast iron by the use of the open- 
hearth finery. In 1784 Cort patented the pud- 
dling process, and in so doing laid the foundation 
of much of the prosperity of England during the 
century that followed. But in recent years 
the whole system of the manufacture of wrought 
iron has been revolutionised by the magnificent 
inventions of Bessemer and Siemens, by which 
the decarburised iron is obtained in the fluid 
condition. The metal then is commonly known 
as ' mUd steel,' and has met with such a variety 
of applications that for rails, girders, guns, ship- 
building, bridge cottstruotion, and many other 
uses, it has gradually replaced the iron obtained 
by the puddUng process. 



Chief Iron ores. Iron is Qccasionally found 
native, either in the form of meteorites ^o con- 
taining nickel, oi as metal which, by the action 
of heat and reducing agents, has been naturally 
separated from the ore. These sources are, 
however, unimportant, except for savage tribes, 
who are in some instances largely dependent 
upon such methods of supply. Iron is very 
widely distributed throughout the crust of the 
earth in various forms. On account of its 
cheapness, and the readiness with which it com- 
bines with various elements, such as sulphur, 
phosphorus, or arsenic, which, if present in the 
metalj would injuriously aSect its mechanical 
properties, comparatively few ferruginous com- 
pounds are practically available as sources of 
iron. It is necessary if an iron ore is to be 
profitably employed that the working expenses 
and carriage should be small, that the ore should 
be rich and readily reduced, and that it should 
be free from sulphur, phosphorus, arsenic, or 
other impurities which seriously deteriorate the 
quality of the iron. Such ores are practically 
either oxides or carbonates. 

Oxides of Iron, These may be divided into 
three classes. 

1. Magnetites. Magnetic oxide of iron 
(FejOj) is the richest oxide of iron which'occurs 
in nature ; if pure, it would contain 72-4 p.c. of 
metallic iron. Its coloui varies from brownish- 
grey to iron-black; it is brittle, magnetic, and 
produces a black streak. It crystamses in the 
cubic system, but is generally found massive. 
It occurs in immense quantities of remarkable 
purity in Sweden and on the shores- of Lake 
Superior. The Swedish iron, which has so long 
been famed, is made from this ore. Ilmenite is 
an impure magnetite containing titanium, 
which occurs in Norway. Franklinite, which 
occurs in New Jersey, may be regarded as a 
magnetite in which the ferrous oxide is more or 
less replaced by oxide of zinc ; and Chrome Iron 
Ore is a magnetite in which the ferric oxide is 
replaced by oxide of chromium. 

2. Bed hcematites. Ferric oxide (FejOg) oc- 
curs in a number of forms which possess dif- 
ferent physical characters, such as Micaceous 
iron ore. Specular iron ore. Kidney iron stone, 
&c. These forms difiei in hardness, density, 
and colour, but each gives a red streak. Bed 
hsematite is generally very free from phosphorus, 
and is found in Cumberland, where it is employed 
in the preparation of a pig iron low in phos- 
phorus, suitable foi the ordinary, or acid, 
Bessemer process. In the United States a 
deposit of phosphorio fed fossil (hsematite) ore 
runs from Clinton in the State of New York to 
Birmingham in Alabama. Many of the ores of 
Spain and of the Lake Superior district, such 
as those of Vermillion, are idso red hematites. 

3. Brown hcematites. Ferric oxide occurs 
associated with a variable amount of combined 
water in the different varieties of brown haema- 
tites. In colour these vary from light to dark 
brown, and'they give a brown streak. A speci- 
ally rich, pure, and easily reducible variety is 
now imported in large quantities from Spain, 
and a pure variety was formerly worked in 
the Forest of Dean. In Northamptonshire, 
Lincolnshire, &c., a brown hssmatite is employed 
which contains about 10 p.c. of silica and over 
0-5 p.c. of phosphorus. The minette ores of 



IRON. 



163 



France and Northern Oermany, in the Ticinity 
of the Bhine, although phosphorio, and containing 
only about 30 p.c. of iron, are of this class, and 
are among the most important iron ore deposits 
of the world. Brown ores are also met with in 
considerable quantities in the United States. 
Limonile, Bog iron ores, and Lahe ores are other 
examples of hydrated oxides of iron occurring in 
various localities. 

Carbonates. These consist essentially of 
ferrous carbonate (FeCO,), the important differ- 
ences in character observed in various ores de- 
pending chiefly upon the amount and character 
of the impurities present. These ores are widely 
distributed and of great importance. 

Spathic irort ore is the purest form in which 
ferrous carbonate occurs ; it has a pearly lustre, 
and is generally light brown in colour. There 
are very extensive deposits of this ore in various 
parts of Europe, notably at Erzberg in Styria ; 
the ore is usually free from phosphorus, but 
contains much manganese. 

Clay iron stone is a less pure variety of 
ferrous carbonate which contains clayey matter, 
and was foi many years the most important 
ore of this country; it usually occurs in the 
coal measures. The ore is generally dark in 
colour, and contains from 30 to 40 p.c. of metallic 
iron, associated with less manganesi» and more 
phosphorus than in the puree spathic ores. 

Cleveland iron stone is a variety of clay iron 
stone met with in the North Biding of Yorkshire. 
It is generally uniform in character and contains 
about 33 p.c. of metallic iron ; it contains little 
manganese, but the percentage of phosphorus is 



highei than in eithes of the ores previously 
mentioned, except, perhaps, in the case of the 
impure brown hsematites. 

Black band iron stone ia an ore which occurs 
(Chiefly in Scotland and North Stafiordshire. It 
contains a variable amount of bituminous matter 
which imparts a characteristic black colour, and 
which frequently enables the ore to be calcined 
vrithout the addition of any extra fuel. In other 
respects black band very closely resembles clay 
iron stone. 

In addition to the ores previously enume- 
rated, several other materials are employed for 
the production of iron, such as ' tap-cinder,' 
which is essentially ferrous silicate, and is pro- 
duced in the puddling process. In this case 
the product obtained is a common variety of 
iron known as cinder pig. Tap-cindm is only 
met with in quantities suitable for the require- 
ments of blast furnaces in those districts 
where puddling has been conducted for a con- 
siderable period. The residue from Spanish 
pyrites, after the extraction of sulphur and cop- 
per, is commonly known as ' purple ore,' and 
has been made into bricks and used in the blast 
furnace. It is often used as a fettling in the 
puddling process. 

The following table will illustrate the ap- 
proximate composition of the various ores of 
iron. It will be understood, of course, that 
such materials are subject to considerable 
variations in character, and it has been thought 
better to give approximate values deduced from 
a number of analyses, than to introduce a mass 
of figures detailing actual results obtained. 



Appeoximath Composition ot Ieon Okbs. 



^ 


Magne- 
tite 


Red hffl- 
matite 


~ Brown hsBmatite 


Carbonate ores 


Lake 
Superior 

■ore 
(Mesabi) 


North- 
ampton 


Spathic 


Clay 
band 


Cleve- 
land 


Black- 
band 


Ferric oxide (FesO,) 
Ferrous oxide (FeO) 
Manganous oxide (MnO) 
Carbon dioxide (GOj) . 
Smca(SiOj) ., . 
Alumma (AljOj) . 
Lime (CaO) .... 
Magnesia (MgO) . 
Phosphorus pentoxide (PaOj) 
Water .... 
Organic matter . 


65 
25 

10 

trace 


90 

1 

1 
1 

trace 


( 85 1 

6 

2-5 ■ 

0-75 

0-5 

0-22 

5 


65 

0-3 

13 
3 

variable 

1-3 
14 


50 

10 

38 

2 

trace 


0-5 
47 

2 
30 
10 

6 

2 

2 

0-6 

1 
trace 


3 

40 

1 
25 

8 

7 
■ 7 

4 

1-5 

2 
trace 


3 

41 

1 
26 

7 

3 

2 

1 

0-6 

1 
15 



Preparation of iron ores. — The greater part 
of the iron ores now raised are charged into the 
blast furnace without any special preparation. 
Anhydrous oxides, such as Lake Superior ores, 
do not require calcination, except in some cases, 
to remove sulphur. The chief European ores 
are, however, treated before smelting. The 
mechanical preparation of iron ores is very 
simple, and consists of a rough assortment of 
the size of the materials to be employed. In 
some cases the larger pieces are broken by hand 
01 suitable crushing machinery, wlulst in other 
instances the very fine ore is separated by 
riddles and used for other purposes, as it would 



be apt to choke up the blast furnace. Poor ores, 
such as those of Cleveland, are charged in larger 
pieces than the richer hsematities or magnetites. 
Non-calcareous ores, which contain iron pyrites, 
are frequently weathered for a few months, and 
the sulphur becoming oxidised, passes away in 
solution as ferrous sulphate. Shale is also 
removed by weathering. 

Calcination. — Many iron ores are calcined 
before being used in the blast furnace, the ob- 
ject being to remove volatile substances such as 
sulphur, water, carbon dioxide, arsenic, &o., and 
to concentrate the iron in the residue. Two 
other important objects are also gained by 



164 



raoN. 



calcination ; in the fiist place the iron is oxidised 
from the ferious to the ferric condition, which 
prevents the formation of scouring slags, rich in 
ferrous sUicate, during reduction in the blast 
furnace ; and further, the material is rendered 
much more porous so that it is more readily 
acted upon by the gases of the furnace. From 
the above remarks it will be evident that some 
ores, such as red haematites, do not require cal- 
cination. Ores which are in a state of fine 
division, such as much of the ore from the Lake 
Superior district, are not calcined. Fine ores 
are frequently briquetted, and the briquettes 
are generally calcined before use in the blast 
furnace. When calcining, it is necessary to 
regulate the temperature as carefully as possible ; 
with low temperatures the ore is insufficiently 
calcined, whilst if the heat be too great, or too 
much fuel is employed, the materials clot together 
and much of the benefit otherwise obtained is 
thus lost. Calcination is often conducted in 
open heaps, or between rectangular walls, 
exactly as in the case of many ores of other 
metals ; but these methods are costly in fuel, 
space, and labour, and are apt to give irregular 
results, so are chiefly used for roasting tap- 
cinder in Staffordshire, or the black bands of 
North Staffordshire and Scotland, in which 
latter case the ore itself contains the necessary 
fuel. Kilns are now very generally employed 
for calcining, and in the Cleveland district the 
use of large circular kilns, constructed of iron 
lined with firebrick, is almost universal. In 
such kilns the ore and fuel are charged in at the 
top, and the calcined material removed from the 
bottom, the operation being continuous; in 
such kilns calcination is well under control, fuel 
is economised, and labour is saved. Bectangulai 
Idlns, fired with surplus gas from the blast 
furnace, have been introduced both in the 
United Kingdom and elsewhere. 

Produelion of pig iron. — ^The ore, having if 
necessary been prepared as before described, is 
now ameUed in the llaH furnace to produce pig 
iron. For this purpose it is introduced at the 
top of the furnace together with the fiux neces- 
sary to form a fluid slag (oi ' cinder ) with the 
gangue of the ore ; fud is also added in sufficient 
quantity to melt the materials and to reduce 
tko iron. The aii necessary for combustion is 
introduced near the bottom of the furnace, 
having been blown, and usually also heated, by 
suitable appliances. The operation is continuous, 
a furnace frequently working without any im- 
portant stoppage for a number of years. The 
whole of the materials introduced into the fur- 
nace have either to be melted and flow off from 
the bottom as iron and cinder, or to be converted 
into vapour and pass off as ' waste gases ' from 
the top. 

The blast furnace. — The earliest form of 
blast furnace is shown in Fig. 1, which represents 
a form employed on the Continent for the pro- 
duction of wrought iron about 600 years ago. 
After the furnace had been heated, ore and fuel 
were introduced at the top, and blast from below ; 
the result was the production of a bloom of 
wrought iron, which, owing to the low tempera- 
tures of such fiunaces, was never melted, but was 
removed by taking down the brickwork at the 
front of the furnace. Doubtless in some of the 
larger furnaces of this description cast iron 



would sometimes be accidentally obtained, and 
as the value of this material for castings, and 
for the direct production of wrought iron by 
means of the finery came to be recognised, cast 
iron would be regularly made. This change was 
probably introduced early in the 16th century, 
and the furnaces gradually increased in size 
until they were capable of producing about 
20 tons of pig iron per week, using charcoal for 
fuel. About 180 years ago coke was introduced 
as fuel in the blast furnace, and the size and 
production were slightly increased. Since this 




period enormous changes have been introduced, 
commencing with the use of coke about 1735 ; 
of hot blast in Scotland in 1S29 ; the adoption 
of round and larger hearths in Sonth StaSor(^hire 
about 1835 ; the utilisation of the waste gases ; 
the largely increased height and capacity 
adopted in the Cleveland district shortly after 
1860, and the use of hot blast stoves on the 
regenerative principle. A remarkable develop- 
ment took place in West Pennsylvania about 
1890, and as a result of easily reducible ores, 
smallei and steeper furnaces, higher blast 
pressure, and increased engine power, a weekly 
production of nearly 6000 tons of pig iron per 
furnace has been attained. Fie. 2 represents a 
Cleveland blast furnace, the height of which 
would be about 80 feet, its capacity about 
25,600 cub. ft., and the weekly production of 
pig iron varying from 600 to about 1000 tons, 
according to the character of the ore used, the 
temperature and pressure of the blast, and 
other circumstances. Such a furnace is closed 
at the top by means of the < cup and cone ' 
arrangement, into which the materials are 
charged, and delivered into the furnace at 
suitable intervals by lowering the moveable 
cone. The combustible gases are conducted 
by means of suitable pipes to the regenera- 
tive stoves employed for heating the blast,- or 
to the boilers required for raising steam for the 
works. A portion of the gases is carefully 
cleaned from dust and used for power purposes 
in gas engines. The furnace its^ is very light 
in construction for so large an erection, which 



IRON. 



165 



ia intended to contain a great weight and to 
resist a very high temperatuie. The outeii 
casing is of iron plates riveted together, and 
the furnace ia lined with refractory firebrick. 
The blast is delivered into the furnace by about 
six twyers, which are connected with the hot 
blast main, and which are water-jacl^eted where 
they enter the furnace to prevent them being 



.I5-0 n 




^ftAmi^ ^& 



Fio. 2. 

rapidly destr